How to Use PHP's array_keys() Function to Retrieve Array Keys

Arrays are a common data type in PHP, and developers often need to obtain their keys; PHP provides the array_keys() function for this purpose.

Syntax :

<code>array_keys ( array $array , mixed $search_value = null , bool $strict = false )</code>

Parameters :

$array : The array whose keys you want to retrieve.

$search_value (optional): If provided, only keys of elements matching this value are returned; default is null .

$strict (optional): When set to true , the function uses strict comparison ( === ) for the search value; default is false .

Return value : An indexed array containing the keys that match the criteria.

Practical examples :

a. Only one parameter :

<code>&lt;?php
$ace = array("one", "two", "three", "four", "Three");
print_r(array_keys($ace));
?&gt;</code>

Output:

<code>Array ( [0] => 0 [1] => 1 [2] => 2 [3] => 3 [4] => 4 )</code>

b. Two parameters (search value) :

<code>&lt;?php
$ace = array("one", "two", "three", "four", "Three");
print_r(array_keys($ace, "three"));
?&gt;</code>

Output:

<code>Array ( [0] => 2 )</code>

c. Three parameters (search value with strict comparison) :

<code>&lt;?php
$ace2 = array("one", "two", "three", "four", "10", 10);
print_r(array_keys($ace2, "10"));
echo "<br>";
print_r(array_keys($ace2, "10", true));
?&gt;</code>

Output:

<code>Array ( [0] => 4 [1] => 5 )
Array ( [0] => 4 )</code>

When the third parameter $strict is set to true , the function performs a strict comparison, distinguishing between the string "10" and the integer 10 .

For the full article, click the "Read Original" link in the source.