How to find the index of an element in an array using PHP ?
In this article, we will discuss how to find the index of an element in an array in PHP. Array indexing starts from 0 to n-1.
Here we have some common approaches
Table of Content
Using array_search() Function
We can get the array index by using the array_search() function. This function is used to search for the given element. It will accept two parameters.
Syntax:
array_search('element', $array)Parameters:
- The first one is the element present in the array.
- The second is the array name.
Return Value: It returns the index number which is an Integer.
Note: We will get the index from indexed arrays and associative arrays.
Example 1: PHP program to get the index of the certain elements from the indexed array.
<?php
// Create an indexed array with 5 subjects
$array1 = array('php', 'java',
'css/html', 'python', 'c/c++');
// Get the index of PHP
echo array_search('php', $array1);
echo "\n";
// Get the index of java
echo array_search('java', $array1);
echo "\n";
// Get the index of c/c++
echo array_search('c/c++', $array1);
echo "\n";
?>
Output
0 1 4
Example 2: The following example returns the index of an associative array.
<?php
// Create an associative array
// with 5 subjects
$array1 = array(
0 => 'php',
1 => 'java',
2 => 'css/html',
3 => 'python',
4 => 'c/c++'
);
// Get the index of php
echo array_search('php', $array1);
echo "\n";
// Get the index of java
echo array_search('java', $array1);
echo "\n";
// Get index of c/c++
echo array_search('c/c++', $array1);
echo "\n";
?>
Output
0 1 4
Using array_flip()
The array_flip() function swaps keys and values in an array. You can use it to find the index of an element by flipping the array and checking if the element exists as a key. If it exists, its value will be the original index.
Example:
<?php
// Create an indexed array with 5 subjects
$array1 = array('php', 'java', 'css/html', 'python', 'c/c++');
// Flip the array
$flippedArray = array_flip($array1);
// Get the index of PHP
if (isset($flippedArray['php'])) {
echo $flippedArray['php'];
} else {
echo "'php' not found in array";
}
echo "\n";
// Get the index of java
if (isset($flippedArray['java'])) {
echo $flippedArray['java'];
} else {
echo "'java' not found in array";
}
echo "\n";
// Get the index of c/c++
if (isset($flippedArray['c/c++'])) {
echo $flippedArray['c/c++'];
} else {
echo "'c/c++' not found in array";
}
echo "\n";
?>
Output
0 1 4
Using a custom function
We can create a custom function to iterate through the array and return the index of the desired element. This approach involves using a simple loop to check each element of the array.
Example: In this custom function, we use a foreach loop to iterate through the array. For each iteration, we check if the current element matches the given element. If a match is found, we return the index (or key) of the element. If no match is found after the loop completes, we return -1 to indicate that the element is not present in the array.
<?php
function findIndex($array, $element) {
foreach ($array as $index => $value) {
if ($value === $element) {
return $index;
}
}
return -1; // Return -1 if the element is not found
}
// Example usage for indexed array
$indexedArray = array('apple', 'banana', 'cherry', 'date');
$index = findIndex($indexedArray, 'cherry');
echo " The index of 'cherry' is: " . $index;
echo "\n";// Output: The index of 'cherry' is: 2
// Example usage for associative array
$assocArray = array('a' => 'apple', 'b' => 'banana', 'c' => 'cherry', 'd' => 'date');
$index = findIndex($assocArray, 'cherry');
echo "The index of 'cherry' is: " . $index; // Output: The index of 'cherry' is: c
?>
Output
The index of 'cherry' is: 2 The index of 'cherry' is: c
Using a foreach Loop
Using a loop to find the index of an element involves iterating through the array with a foreach loop. Check each value, and if it matches the target element, store the current key as the index and exit the loop. This method ensures a manual search.
Example
<?php
$array = array("apple", "banana", "cherry");
$value = "banana";
$index = null;
foreach ($array as $key => $val) {
if ($val === $value) {
$index = $key;
break;
}
}
if ($index !== null) {
echo "The index of '$value' is $index.\n";
} else {
echo "'$value' is not found in the array.\n";
}
?>
Output
The index of 'banana' is 1.
Using array_keys Function
The array_keys function in PHP returns all keys of an array that match a specified value. By passing the value you want to find, you get an array of matching keys. Use `[0]` to get the first index if multiple matches exist.
Example:
<?php
$array = ['apple', 'banana', 'cherry', 'banana'];
$elementToFind = 'banana';
// Find all keys that match the value
$keys = array_keys($array, $elementToFind);
if (!empty($keys)) {
echo "The element '$elementToFind' is found at indices: " . implode(', ', $keys);
} else {
echo "The element '$elementToFind' was not found in the array.";
}
?>
Output
The element 'banana' is found at indices: 1, 3
Using array_map() Function
The array_map() function applies a callback function to each element of the array, allowing you to transform the array elements before searching for the index. This can be useful if you need to perform case-insensitive searches or other custom operations on the array elements.
Example: In this example, we use array_map() to convert all elements to lowercase before searching for the index of a particular element. This makes the search case-insensitive.
<?php
// Create an indexed array with mixed case elements
$array = array('Apple', 'Banana', 'Cherry', 'Date');
// Convert all elements to lowercase
$lowercaseArray = array_map('strtolower', $array);
// Search for the lowercase version of the element
$elementToFind = 'banana';
$index = array_search(strtolower($elementToFind), $lowercaseArray);
if ($index !== false) {
echo "The index of '$elementToFind' is: $index";
} else {
echo "'$elementToFind' was not found in the array";
}
?>
Output
The index of 'banana' is: 1
This approach is flexible because it allows you to manipulate the array elements before performing the search, making it adaptable to various use cases like case-insensitive searches, trimming whitespace, or applying other transformations.
