Get the index of a certain value in an array in PHP
PhpArraysPhp Problem Overview
I have an array:
$list = array('string1', 'string2', 'string3');
I want to get the index for a given value (i.e. 1
for string2
and 2
for string3
)
All I want is the position of the strings in the array
- string1 is 0
- string2 is 1
- string3 is 2
How to achieve this?
Php Solutions
Solution 1 - Php
array_search
is the way to do it.
> array_search ( mixed $needle , array $haystack [, bool $strict = FALSE ] ) : mixed
From the docs:
$array = array(0 => 'blue', 1 => 'red', 2 => 'green', 3 => 'red');
$key = array_search('green', $array); // $key = 2;
$key = array_search('red', $array); // $key = 1;
You could loop over the array manually and find the index but why do it when there's a function for that. This function always returns a key and it will work well with associative and normal arrays.
Solution 2 - Php
If you're only doing a few of them (and/or the array size is large), then you were on the right track with array_search:
$list = array('string1', 'string2', 'string3');
$k = array_search('string2', $list); //$k = 1;
If you want all (or a lot of them), a loop will prob do you better:
foreach ($list as $key => $value) {
echo $value . " in " . $key . ", ";
}
// Prints "string1 in 0, string2 in 1, string3 in 2, "
Solution 3 - Php
Other folks have suggested array_search()
which gives the key of the array element where the value is found. You can ensure that the array keys are contiguous integers by using array_values()
:
$list = array(0=>'string1', 'foo'=>'string2', 42=>'string3');
$index = array_search('string2', array_values($list));
print "$index\n";
// result: 1
You said in your question that array_search()
was no use. Can you explain why? What did you try and how did it not meet your needs?
Solution 4 - Php
The problem is that you don't have a numerical index on your array.
Using array_values() will create a zero indexed array that you can then search using array_search() bypassing the need to use a for loop.
$list = ['string1', 'string2', 'string3'];
$index = array_search('string2',array_values($list));
Solution 5 - Php
// or considering your array structure:
$array = array(
'string1' => array('a' => '', 'b' => '', 'c' => ''),
'string2' => array('a' => '', 'b' => '', 'c' => ''),
'string3' => array('a' => '', 'b' => '', 'c' => ''),
);
// you could just
function findIndexOfKey($key_to_index,$array){
return array_search($key_to_index,array_keys($array));
}
// executed
print "\r\n//-- Method 1 --//\r\n";
print '#index of: string1 = '.findIndexofKey('string1',$array)."\r\n";
print '#index of: string2 = '.findIndexofKey('string2',$array)."\r\n";
print '#index of: string3 = '.findIndexofKey('string3',$array)."\r\n";
// alternatively
print "\r\n//-- Method 2 --//\r\n";
print '#index of: string1 = '.array_search('string1',array_keys($array))."\r\n";
print '#index of: string2 = '.array_search('string2',array_keys($array))."\r\n";
print '#index of: string3 = '.array_search('string3',array_keys($array))."\r\n";
// recursersively
print "\r\n//-- Method 3 --//\r\n";
foreach(array_keys($array) as $key => $value){
print '#index of: '.$value.' = '.$key."\r\n";
}
// outputs
//-- Method 1 --//
#index of: string1 = 0
#index of: string2 = 1
#index of: string3 = 2
//-- Method 2 --//
#index of: string1 = 0
#index of: string2 = 1
#index of: string3 = 2
//-- Method 3 --//
#index of: string1 = 0
#index of: string2 = 1
#index of: string3 = 2
Solution 6 - Php
Try the array_keys PHP function.
$key_string1 = array_keys($list, 'string1');
Solution 7 - Php
Could you be a little more specific?
$key = array_search('string2',$list)
works fine for me. Are you trying to accomplish something more complex?
Solution 8 - Php
This code should do the same as your new routine, working with the correct multi-dimensional array..
$arr = array(
'string1' => array('a' => '', 'b' => '', 'c' => ''),
'string2' => array('a' => '', 'b' => '', 'c' => ''),
'string3' => array('a' => '', 'b' => '', 'c' => '')
);
echo 'Index of "string2" = '. array_search('string2', array_keys($arr));
Solution 9 - Php
array_search should work fine, just tested this and it returns the keys as expected:
$list = array('string1', 'string2', 'string3');
echo "Key = ".array_search('string1', $list);
echo " Key = ".array_search('string2', $list);
echo " Key = ".array_search('string3', $list);
Or for the index, you could use
$list = array('string1', 'string2', 'string3');
echo "Index = ".array_search('string1', array_merge($list));
echo " Index = ".array_search('string2', array_merge($list));
echo " Index = ".array_search('string3', array_merge($list));
Solution 10 - Php
$find="Topsite";
$list=array("Tope","Ajayi","Topsite","Infotech");
$list_count=count($list);
sort($list);
for($i=0;$i<$list_count;$i++)
{
if($list[$i]==$find){
$position=$i;
}
}
echo $position;
Solution 11 - Php
You'll have to create a function for this. I don't think there is any built-in function for that purpose. All PHP arrays are associative by default. So, if you are unsure about their keys, here is the code:
<?php
$given_array = array('Monday' => 'boring',
'Friday' => 'yay',
'boring',
'Sunday' => 'fun',
7 => 'boring',
'Saturday' => 'yay fun',
'Wednesday' => 'boring',
'my life' => 'boring');
$repeating_value = "boring";
function array_value_positions($array, $value){
$index = 0;
$value_array = array();
foreach($array as $v){
if($value == $v){
$value_array[$index] = $value;
}
$index++;
}
return $value_array;
}
$value_array = array_value_positions($given_array, $repeating_value);
$result = "The value '$value_array[0]' was found at these indices in the given array: ";
$key_string = implode(', ',array_keys($value_array));
echo $result . $key_string . "\n";//Output: The value 'boring' was found at these indices in the given array: 0, 2, 4, 6, 7
Solution 12 - Php
Here is a function that will work for numeric or string indices. Pass the array as first parameter, then the index to the element that needs to be moved and finally set the direction to -1 to move the element up and to 1 to move it down. Example: Move(['first'=>'Peter','second'=>'Paul','third'=>'Kate'],'second',-1) will move Paul up and Peter down.
function Move($a,$element,$direction)
{
$temp = [];
$index = 0;
foreach($a as $key=>$value)
{
$temp[$index++] = $key;
}
$index = array_search($element,$temp);
$newpos = $index+$direction;
if(isset($temp[$newpos]))
{
$value2 = $temp[$newpos];
$temp[$newpos]=$element;
$temp[$index]=$value2;
}
else
{
# move is not possible
return $a; # returns the array unchanged
}
$final = [];
foreach($temp as $next)
{
$final[$next]=$a[$next];
}
return $final;
}