It seems to be limited only by the script&#39;s memory limit.

A quick test got me a key of 128mb no problem:

    ini_set(&#39;memory_limit&#39;, &#39;1024M&#39;);
    
    $key = str_repeat(&#39;x&#39;, 1024 * 1024 * 128);
    
    $foo = array($key =&gt; $key);
    
    echo strlen(key($foo)) . &quot;&lt;br&gt;&quot;;
    echo strlen($foo[$key]) . &quot;&lt;br&gt;&quot;;

There is no practical limit to string size in PHP. According to [the manual][1]:

&gt; Note: It is no problem for a string to
&gt; become very large. PHP imposes no
&gt; boundary on the size of a string; the
&gt; only limit is the available memory of
&gt; the computer on which PHP is running.

It is safe to assume that this would apply to using strings as keys in arrays as well, but depending on how PHP handles its lookups, you may notice a performance hit as strings get larger.

  [1]: http://us.php.net/manual/en/language.types.string.php

In zend_hash.h, you can find `zend_inline_hash_func()` method that can show how to hash key string in PHP, So use key which string length less than 8 characters is better for performance.

    static inline ulong zend_inline_hash_func(char *arKey, uint nKeyLength) {

    register ulong hash = 5381;
 
    /* variant with the hash unrolled eight times */
    for (; nKeyLength &gt;= 8; nKeyLength -= 8) {
        hash = ((hash &lt;&lt; 5) + hash) + *arKey++;
        hash = ((hash &lt;&lt; 5) + hash) + *arKey++;
        hash = ((hash &lt;&lt; 5) + hash) + *arKey++;
        hash = ((hash &lt;&lt; 5) + hash) + *arKey++;
        hash = ((hash &lt;&lt; 5) + hash) + *arKey++;
        hash = ((hash &lt;&lt; 5) + hash) + *arKey++;
        hash = ((hash &lt;&lt; 5) + hash) + *arKey++;
        hash = ((hash &lt;&lt; 5) + hash) + *arKey++;
    }
    switch (nKeyLength) {
        case 7: hash = ((hash &lt;&lt; 5) + hash) + *arKey++; /* fallthrough... */
        case 6: hash = ((hash &lt;&lt; 5) + hash) + *arKey++; /* fallthrough... */
        case 5: hash = ((hash &lt;&lt; 5) + hash) + *arKey++; /* fallthrough... */
        case 4: hash = ((hash &lt;&lt; 5) + hash) + *arKey++; /* fallthrough... */
        case 3: hash = ((hash &lt;&lt; 5) + hash) + *arKey++; /* fallthrough... */
        case 2: hash = ((hash &lt;&lt; 5) + hash) + *arKey++; /* fallthrough... */
        case 1: hash = ((hash &lt;&lt; 5) + hash) + *arKey++; break;
        case 0: break;  EMPTY_SWITCH_DEFAULT_CASE()
    }
        return hash;   
    }

I want to wait for a process to finish, but `process.WaitForExit()` hangs my GUI.  Is there an event-based way, or do I need to spawn a thread to block until exit, then delegate the event myself?

process.WaitForExit() asynchronously

I am currently working on a REST library for .net, and I would like to hear some opinions about an open point I have:  REST and authentication.

Here is an example of an RESTful interface used with the library:

    [RestRoot(&quot;/user&quot;)]
    public interface IUserInterface
    {
      [RestPut(&quot;/&quot;)]
      void Add(User user);

      [RestGet(&quot;/&quot;)]
      int[] List();

      [RestGet(&quot;/get/{id}&quot;)]
      User Get(int id);

      [RestDelete(&quot;/delete/{id}&quot;)]
      void Delete(int id);
    }
	
The server code then just implements the interface and the clients can obtain the same interface through a factory. Or if the client is not using the library a standard HTTP request also works.

I know that there are the major ways of either using HTTP Basic Auth or sending a token to requests requiring authenticated users.

The first method (HTTP Basic Auth), has the following issues (partly web browser specific):

- The password is transmitted with every request - even with SSL this has some kind of &quot;bad feeling&quot;.
- Since the password is transmitted with a request header, it would be easy for an local attacker to look at the transmitted headers to gain the password.
- The password is available in the browsers memory.
- No standard way to expire user &quot;sessions&quot;.
- Login with a browser interrupts the look and feel of a page.
 
The issues for the second method are more focused on implementation and library use:

- Each request URI which needs authentication must have a parameter for the token, which is just very repetitive.
- There is a lot more code to write if each method implementation needs to check if a token is valid.
- The interface will become less specific e.g. `[RestGet(&quot;/get/{id}&quot;)]` vs. `[RestGet(&quot;/get/{id}/{token}&quot;)]`.
- Where to put the token: at the end of the URI? after the root? somewhere else?

----------

My idea was to pass the token as parameter to the URL like `http:/server/user/get/1234?token=token_id`.

Another possibility would be to send the parameter as an HTTP header, but this would complicate usage with plain HTTP clients I guess.

The token would get passed back to the client as a custom HTTP header (&quot;X-Session-Id&quot;) on each request.

This then could be completely abstracted from the interface, and any implementation needing authentication could just ask which user the token (if given) belongs to.

Do you think this would violate REST too much or do you have any better ideas?

REST and authentication variants

I am generating associative arrays and the key value is a string concat of 1..n columns.

Is there a max length for keys that will come back to bite me? If so, I&#39;ll probably stop and do it differently.

What is the max key size for an array in PHP?

<p>I am generating associative arrays and the key value is a string concat of 1..n columns.</p>
<p>Is there a max length for keys that will come back to bite me? If so, I'll probably stop and do it differently.</p>


What libraries, extensions etc. would be required to render a portion of a PDF document to an image file?

Most PHP PDF libraries that I have found center around creating PDF documents, but is there a simple way to render a document to an image format suitable for web use?

Our environment is a LAMP stack.

How do I convert a PDF document to a preview image in PHP?

I want to create a static class in PHP and have it behave like it does in C#, so

 1. Constructor is automatically called on the first call to the class
 2. No instantiation required

Something of this sort...

    static class Hello {
        private static $greeting = &#39;Hello&#39;;
    
        private __construct() {
            $greeting .= &#39; There!&#39;;
        }
    
        public static greet(){
            echo $greeting;
        }
    }
    
    Hello::greet(); // Hello There!



Is it possible to create static classes in PHP (like in C#)?

Which PHP function can return the current date/time?


How do I get the current date and time in PHP?

Anyone know how can I post a SOAP Request from PHP?

How to post SOAP Request from PHP

How to get directory size in PHP

**Edit:** I apologize everybody. I used the term &quot;jagged array&quot; when I actually meant to say &quot;multi-dimensional array&quot; (as can be seen in my example below). I apologize for using the incorrect name. I actually found jagged arrays to be faster than multi-dimensional ones! I have added my measurements for jagged arrays.

I was trying to use a &lt;del&gt;jagged&lt;/del&gt; multi-dimensional array today, when I noticed that it&#39;s performance is not as I would have expected. Using a single-dimensional array and manually calculating indices was much faster (almost two times) than using a 2D array. I wrote a test using  `1024*1024` arrays (initialized to random values), for 1000 iterations, and I got the following results on my machine:

    sum(double[], int): 2738 ms (100%)
    sum(double[,]):     5019 ms (183%)
    sum(double[][]):    2540 ms ( 93%)

This is my test code:

    public static double sum(double[] d, int l1) {
        // assuming the array is rectangular
        double sum = 0;
        int l2 = d.Length / l1;
        for (int i = 0; i &lt; l1; ++i)
            for (int j = 0; j &lt; l2; ++j)
                sum += d[i * l2 + j];
        return sum;
    }

    public static double sum(double[,] d) {
        double sum = 0;
        int l1 = d.GetLength(0);
        int l2 = d.GetLength(1);
        for (int i = 0; i &lt; l1; ++i)
            for (int j = 0; j &lt; l2; ++j)
                sum += d[i, j];
        return sum;
    }

    public static double sum(double[][] d) {
        double sum = 0;
        for (int i = 0; i &lt; d.Length; ++i)
            for (int j = 0; j &lt; d[i].Length; ++j)
                sum += d[i][j];
        return sum;
    }

    public static void Main() {
        Random random = new Random();
        const int l1  = 1024, l2 = 1024;
        double[ ] d1  = new double[l1 * l2];
        double[,] d2  = new double[l1 , l2];
        double[][] d3 = new double[l1][];

        for (int i = 0; i &lt; l1; ++i) {
            d3[i] = new double[l2];
            for (int j = 0; j &lt; l2; ++j)
                d3[i][j] = d2[i, j] = d1[i * l2 + j] = random.NextDouble();
        }
        //
        const int iterations = 1000;
        TestTime(sum, d1, l1, iterations);
        TestTime(sum, d2, iterations);
        TestTime(sum, d3, iterations);
    }

Further investigation showed that the IL for the second method is 23% larger than that of the first method. (Code size 68 vs 52.) This is mostly due to calls to `System.Array::GetLength(int)`. The compiler also emits calls to `Array::Get` for the &lt;del&gt;jagged&lt;/del&gt; multi-dimensional array, whereas it simply calls `ldelem` for the simple array.

So I am wondering, why is access through multi-dimensional arrays slower than normal arrays? I would have assumed the compiler (or JIT) would do something similar to what I did in my first method, but this was not actually the case.

Could you plese help me understand why this is happening the way it is?

----------

**Update:** Following Henk Holterman&#39;s suggestion, here is the implementation of `TestTime`:

    public static void TestTime&lt;T, TR&gt;(Func&lt;T, TR&gt; action, T obj,
                                       int iterations)
    {
        Stopwatch stopwatch = Stopwatch.StartNew();
        for (int i = 0; i &lt; iterations; ++i)
            action(obj);
        Console.WriteLine(action.Method.Name + &quot; took &quot; + stopwatch.Elapsed);
    }

    public static void TestTime&lt;T1, T2, TR&gt;(Func&lt;T1, T2, TR&gt; action, T1 obj1,
                                            T2 obj2, int iterations)
    {
        Stopwatch stopwatch = Stopwatch.StartNew();
        for (int i = 0; i &lt; iterations; ++i)
            action(obj1, obj2);
        Console.WriteLine(action.Method.Name + &quot; took &quot; + stopwatch.Elapsed);
    }


Why are multi-dimensional arrays in .NET slower than normal arrays?

What&#39;s the easiest way to shuffle an array with python?

Shuffle an array with python, randomize array item order with python

I&#39;m having troubles creating a property of an array of integers in Objective-C.
I&#39;m not sure whether this is even possible to do in Obj-C so I&#39;m hoping someone can help me in finding out either how to do it correctly or provide an alternative solution.

myclass.h

    @interface myClass : NSObject {

	@private int doubleDigits[10];
    }

    @property int doubleDigits;
    @end

myclass.m

    @implementation myClass
    
        @synthesize doubleDigits;
        -(id) init {
        	
        	self = [super init];
        	
        	int doubleDigits[10] = {1,2,3,4,5,6,7,8,9,10};
        	
        	return self;
        }
        
        @end

When I build and run, I get the following error:

&gt; error: type of property &#39;doubleDigits&#39;
&gt; does not match type of ivar
&gt; &#39;doubleDigits&#39;


Create an array of integers property in Objective-C

First off, here is some code:

    int main() 
    {
        int days[] = {1,2,3,4,5};
        int *ptr = days;
        printf(&quot;%u\n&quot;, sizeof(days));
        printf(&quot;%u\n&quot;, sizeof(ptr));
        
        return 0;
    }

Is there a way to find out the size of the array that `ptr` is pointing to (instead of just giving its size, which is four bytes on a 32-bit system)? 


How to find the &#39;sizeof&#39; (a pointer pointing to an array)?

Lets say I have this array,

    int[] numbers = {1, 3, 4, 9, 2};

How can I delete an element by &quot;name&quot;? , lets say number 4?

Even `ArrayList` didn&#39;t help to delete?

    string strNumbers = &quot; 1, 3, 4, 9, 2&quot;;
    ArrayList numbers = new ArrayList(strNumbers.Split(new char[] { &#39;,&#39; }));
    numbers.RemoveAt(numbers.IndexOf(4));
    foreach (var n in numbers)
    {
        Response.Write(n);
    }

How to delete an element from an array in C#

Regarding the C++ STL map, erasing by key:-

     size_type map::erase ( const key_type&amp; x );

Is it legal to erase a non-existing key? i.e. is the snippet below ok?

    map&lt;char,int&gt; mymap;
    mymap[&#39;c&#39;]=30;
    mymap.erase(&#39;c&#39;);
    mymap.erase(&#39;c&#39;);
    mymap.erase(&#39;D&#39;);

Cheers


C++ STL map::erase a non-existing key

What are the differences between PRIMARY, UNIQUE, INDEX and FULLTEXT when creating MySQL tables?

How would I use them?

Differences between INDEX, PRIMARY, UNIQUE, FULLTEXT in MySQL?

I have a Perl script that is counting the number of occurrences of various strings in a text file. I want to be able to check if a certain string is not yet a key in the hash. Is there a better way of doing this altogether?

Here is what I am doing:

    foreach $line (@lines){
        if(($line =~ m|my regex|) )
        {
            $string = $1;
            if ($string is not a key in %strings) # &quot;strings&quot; is an associative array
            {
                $strings{$string} = 1;
            }
            else
            {
                $n = ($strings{$string});
                $strings{$string} = $n +1;
            }
        }
    }


How can I see if a Perl hash already has a certain key?

Do you need to explicitly create an index, or is it implicit when defining the primary key?  Is the answer the same for MyISAM and InnoDB?

Is the primary key automatically indexed in MySQL?

I have a `std::map` that I&#39;m using to store values for x and y coordinates. My data is very sparse, so I don&#39;t want to use arrays or vectors, which would result in a massive waste of memory. My data ranges from -250000 to 250000, but I&#39;ll only have a few thousand points at the most.

Currently I&#39;m creating a `std::string` with the two coordinates (i.e. `&quot;12x45&quot;`) and using it as a key. This doesn&#39;t seem like the best way to do it.

My other thoughts were to use an int64 and shove the two int32s into it and use it as a key.

Or to use a class with the two coordinates. What are the requirements on a class that is to be used as the key?

What is the best way to do this? I&#39;d rather not use a map of maps.

Content Type	Original Author	Original Content on Stackoverflow
Question	Ross	View Question on Stackoverflow
Solution 1 - Php	Greg	View Answer on Stackoverflow
Solution 2 - Php	Lusid	View Answer on Stackoverflow
Solution 3 - Php	Bob Bao	View Answer on Stackoverflow

What is the max key size for an array in PHP?

Php Problem Overview

Php Solutions

Solution 1 - Php

Solution 2 - Php

Solution 3 - Php

REST and authentication variants

process.WaitForExit() asynchronously

Attributions