PHP array_key_first() function

The array_key_first () function in PHP gets the first key of an array if the specified array is not empty.

Syntax

array_key_first(array;$array)

Parameter

array(required)- This parameter signifies the input array.

Return

This function returns the first key of the specified array if the array is not empty else it returns NULL.

Example 1

 1, 'second' => 2, 'third' => 3,'fourth' => 4];
echo("Array : \n");
var_export($array);
//will return the first key for $array
$firstKey = array_key_first($array);
//printing the returned value
echo("\nThe first key is ");
var_dump($firstKey);
?> 

Output

Array: 
array (
  'first' => 1,
  'second' => 2,
  'third' => 3,
  'fourth' => 4,
)
The first key is string(5) "first" 

Example 2

 96, 'Harshit' => 94, 'Sapna' => 93,'Chandhan' => 92];
echo("Student Array : \n");
var_export($student_array);
//will return the first key for $array
$firstKey = array_key_first($student_array);
//printing the returned value
echo("\nThe topper of the class is ");
var_dump($firstKey);
?> 

Output

Student Array: 
array (
  'Reema' => 96,
  'Harshit' => 94,
  'Sapna' => 93,
  'Chandhan' => 92,
)
The topper of the class is string(5) "Reema" 

Example 3

Output

Array: 
'The first key of the array is 0' 

Example 4

'Reema',4 => 'Harshit',3 =>'Sapna'];
echo("Student Array : \n");
var_export($array);
//will return the last key for $array
$firstKey = array_key_first($array);
//printing the returned value
echo("\nThe first element is ");
var_export($firstKey);
// sorting the keys of the arrays in ascending order
ksort($array);
echo("\nNew Array: ");
var_export($array);
echo("\nThe first element is ".array_key_first($array));
?> 

Output

Student Array : 
array (
  9 => 'Reema',
  4 => 'Harshit',
  3 => 'Sapna',
)
The first element is 9
New Array: array (
  3 => 'Sapna',
  4 => 'Harshit',
  9 => 'Reema',
)
The first element is 3