Given a String, the task is to split and join strings in PHP. It is a common operations that allow you to manipulate and manage text data effectively.

Below are the approaches to split and join a string in PHP:

Using explode() and implode() Function

The explode() function is used to split a string into an array based on a delimiter. It is used when you want to break the given string into individual words. The implode() function is used to join array elements into a single string.

• explode(” “, $string) function splits the string into an array using the space character as the delimiter.
• implode(” “, $string) function joins the elements of the array back into a single string using the space character as the delimiter.

Example: This example shows the use of the above-explained approach.

<?php

// Original string
$string = "Hello and Welcome to Geeks for Geeks";

// Splitting the string into individual words
$splitString = explode(" ", $string);
echo "After Splitting\n";
print_r($splitString);

// Joining the array elements
$joinedString = implode("_", $splitString);
echo "\nAfter Joining\n";
echo $joinedString;

?>

After Splitting
Array
(
    [0] => Hello
    [1] => and
    [2] => Welcome
    [3] => to
    [4] => Geeks
    [5] => for
    [6] => Geeks
)

After Joining
Hello_and_Welcome_to_Geeks_for_Geeks

Using str_split() and Custom Join Function

The str_split() function splits a string into an array of characters. For joining, we can create a custom function that concatenates array elements. It will concatenate the array elements into a single string, adding the separator between elements, and returns the resulting string.

Example: This example shows the use of the above-explained approach.

<?php

// Original string
$string = "HelloWorld";

// Split the string into characters
$splitString = str_split($string);

echo "After Splitting\n";
print_r($splitString);

// Custom function to join array elements
function customJoin($array, $separator = "_") {
    $joinedString = "";
    foreach ($array as $element) {
        $joinedString .= $element . $separator;
    }
    return rtrim($joinedString, $separator);
}

// Joining the characters
$joinedString = customJoin($splitString);
echo "\nAfter Joining\n";
echo $joinedString;

?>

After Splitting
Array
(
    [0] => H
    [1] => e
    [2] => l
    [3] => l
    [4] => o
    [5] => W
    [6] => o
    [7] => r
    [8] => l
    [9] => d
)

After Joining
H_e_l_l_o_W_o_r_l_d

Using Regular Expressions with preg_split() and implode() Function

For more complex splitting patterns, you can use regular expressions with the preg_split() function. The implode() function will be used to join array elements into a single string.

• preg_split(“/[\s,]+/”, $string) splits the string $string into an array using a regular expression that matches one or more spaces or commas.

Example: This example shows the use of the above-explained approach.

<?php

// Original string
$string = "Hello and Welcome to GeeksforGeeks";

// Splitting the string using regular expression
$splitString = preg_split("/[\s,]+/", $string);
echo "After Splitting\n";
print_r($splitString);

// Joining the array elements
$joinedString = implode("_", $splitString);
echo "\nAfter Joining\n";
echo $joinedString;

?>

After Splitting
Array
(
    [0] => Hello
    [1] => and
    [2] => Welcome
    [3] => to
    [4] => GeeksforGeeks
)

After Joining
Hello_and_Welcome_to_GeeksforGeeks