In this tutorial, you will learn how to replace characters in a string using PHP. This functionality is essential for manipulating data, cleaning inputs, and creating dynamic output in web applications. PHP offers several built-in functions to perform string replacement operations efficiently, making it easy to replace specific characters, words, or patterns within a string.

Understanding String Replacement in PHP

Performing string replacement means replacing a specific set of characters with another in a given string. This process involves searching for special characters or substrings within a string and replacing them with new characters. For example, you might want to replace all spaces in a string with dashes or replace every occurrence of a particular word with another word.

PHP provides the following built-in functions for string replacement:
  • str_replace()
  • str_ireplace()
  • preg_replace()
  • substr_replace()
  • mb_ereg_replace()
  • mb_eregi_replace()

Using str_replace() Function

The str_replace() function is commonly used to replace characters or substrings in PHP. It searches for a specified value within a string and replaces it with a new one.


str_replace(find, replace, string, count)

To demonstrate how the str_replace() works,  consider the example of replacing spaces with dashes in a sentence:


$url = "Company Profile Page";
$formattedUrl = str_replace(" ", "-", $url);
echo $formattedUrl; // Outputs: "Company-Profile-Page"

Case-insensitive Replacement with str_ireplace()

It's important to note that str_replace() is case-sensitive. If you need to perform case-insensitive replacements, use the str_ireplace() function, which works similarly to str_replace() but ignores case differences.

Replacing Multiple Values with str_replace()

str_replace() is not limited to single characters. You can also replace multiple values simultaneously by passing arrays to the $search and $replace parameters:


// Original notification settings text
$notificationText = "Enable email notifications for updates and offers.";

// Arrays of search and replace values to clarify the notification settings
$searchArray = ["email notifications", "updates", "offers"];
$replaceArray = ["email alerts", "product updates", "special offers"];

// Replace multiple values in the notification settings text
$updatedNotificationText = str_replace($searchArray, $replaceArray, $notificationText);

// Display the updated notification settings text
echo $updatedNotificationText; // Outputs: "Enable email alerts for product updates and special offers."

Using preg_replace() for Patatern-based Replacement

The preg_replace() function offers more flexibility by allowing pattern-based replacements using regular expressions.


preg_replace(pattern, replacement, string, limit, count)


$formattedNumber = "1,234,567";
$cleanNumber = preg_replace('/,/', '', $formattedNumber);
echo $cleanNumber; // Outputs: "1234567"

Using substr_replace() for Position-based Replacement

substr_replace() replaces part of a string with another string based on position.


substr_replace($original, $replacement, $start, $length)


// Original transaction statement
$statement = "Transaction ID 12345: Status - Pending";

// Update the transaction status in the statement
$updatedStatement = substr_replace($statement, "Completed", 31, 7);

// Display the updated transaction statement
echo $updatedStatement; // Outputs: "Transaction ID 12345: Status - Completed"

Multibyte String Replacement with mb_ereg_replace() and mb_eregi_replace()

For multibyte strings and case-insensitive pattern matching, use mb_ereg_replace() and mb_eregi_replace().


mb_ereg_replace($pattern, $replacement, $string, $option = "msr")


// Original welcome message in Japanese
$welcomeMessage = "こんにちは、お元気ですか?";

// Replace the Japanese phrase "お元気ですか?" (how are you?) with an English phrase.
$englishWelcome = mb_ereg_replace("お元気ですか?", "how are you?", $welcomeMessage);

// Display the updated welcome message
echo $englishWelcome; // Outputs: "こんにちは、how are you?"

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