How to replace a text in a string with another text using PHP ?

A string is a sequence of one or more characters. A string is composed of characters, each of which can be replaced easily in the script. A large number of in-built PHP methods can be used to perform string replacements. 

Approach 1: Using str_replace() method - The str_replace()

This method is used to replace a text in the string with another string. However, the method compares the case of the mentioned strings. The string remains unmodified in case the old string is not found with any matchings. 

str_replace($oldString, $newString, $string)

Parameters: 

1. $oldString: It specifies the string to be searched and replaced.
2. $newString: It specifies the string that we want to replace with the $oldString string.
3. $string: It specifies the string or array of strings which we want to search for $oldString and replace with $newString.

Example:

<?php

// Declaring a string variable
$str = "Hi! This is geeksforgeeks";
echo("Original String : ");
echo($str."<br>");

// Old string
$str_old = "This";

// New string
$str_new = "That";

// Replacing part of string
$final_str = str_replace($str_old,$str_new,$str);

echo("Modified String : ");
echo($final_str);

?>

Output:

Original String : Hi! This is geeksforgeeks
Modified String : Hi! That is geeksforgeeks

Note: If a part of the string is found at multiple portions, each instance of the old string is replaced with the new counterpart. The following code snippet illustrates the replacement of the symbol " " with an underscore. 

<?php

// Declaring a string variable
$str = "Hi! This is geeksforgeeks";
echo("Original String : ");
echo($str . "\n");

// Old string
$str_old = " ";

// New string
$str_new = "__";

// Replacing part of string
$final_str = str_ireplace($str_old,$str_new,$str);

echo("Modified String : ");
echo($final_str);

?>

Output:

Original String : Hi! This is geeksforgeeks
Modified String : Hi!__This__is__geeksforgeeks

Approach 2: Using str_ireplace() method

In case, we wish to replace the string irrespective of the case in which the old string is in, the str_ireplace() method is used. The method is supported in PHP 5+. The string behaves in a similar manner as compared to the str_replace() method. 

Syntax:

str_ireplace($oldString, $newString, $string)

Parameters:

• $oldString: The string to locate in the string.
• $newString: The string to replace the old string with.
• $string: The specified string.

<?php

// Declaring a string variable
$str = "Hi! This is geeksforgeeks";

echo("Original String : ");
echo($str . "<br>");

// Old string
$str_old = "GEEKSFoRGEEks";

// New string
$str_new = "GFG";

// Replacing part of string
$final_str = str_ireplace($str_old,$str_new,$str);

echo("Modified String : ");
echo($final_str);

?>

Output:

Original String : Hi! This is geeksforgeeks
Modified String : Hi! This is GFG

Approach 3: Using preg_replace()

Using preg_replace() in PHP, replace text in a string based on a regular expression pattern. It allows for flexible and precise replacements, making it suitable for complex matching and substitutions.

Example:

<?php
$string = "Hello, World!";
$newString = preg_replace('/World/', 'PHP', $string);
echo $newString;
?>

Hello, PHP!

Approach 4: Using substr_replace() method

The substr_replace() method is used to replace a part of a string with another string. This function is useful when you know the position and length of the substring you want to replace.

Example: In this example, we will use the substr_replace method.

<?php

// Declaring a string variable
$str = "Hello, World!";
echo("Original String : ");
echo($str . "\n");

// Replacement string
$replacement = "PHP";

// Starting position
$start = 7;

// Length of the substring to be replaced
$length = 5;

// Replacing part of string
$final_str = substr_replace($str, $replacement, $start, $length);

echo("Modified String : ");
echo($final_str);

?>

Original String : Hello, World!
Modified String : Hello, PHP!

Approach 5: Using strtr() Method

The strtr() function in PHP is another useful method to perform string replacements. This function can replace multiple characters or substrings at once based on a mapping of replacements. It is efficient when dealing with a large number of replacements.

Example:

<?php
$originalString = "Hello World!";
$modifiedString = strtr($originalString, "eo", "ie");
echo "Original String: " . $originalString . "\n";
echo "Modified String: " . $modifiedString;
?>

Original String: Hello World!
Modified String: Hille Werld!