How to Insert Characters in a String at a Certain Position in PHP ? Last Updated : 23 Jul, 2025 Comments Improve Suggest changes Like Article Like Report You will learn how to insert characters into a string at a specific position in PHP. Given a string str and an integer position that describes the index in the original string where the desired string insertStr will be added. This can be achieved using various approaches, such as string concatenation, and the substr_replace() function. Examples:Input: str = "Welcome GeeksforGeeks" insertStr = "to " position = 8 Output: "Welcome to GeeksforGeeks" Input: str = "Hello World" insertStr = "Beautiful " position = 6 Output: Hello Beautiful WorldTable of ContentUsing String ConcatenationUsing substr_replace() FunctionUsing mb_substr() FunctionUsing the str_split() Function1. Using String ConcatenationOne way to insert characters into a string is by splitting the string at the desired position, inserting the required string and then concatenating the parts with the new characters.Example: Implementation of inserting characters in a string at a certain position using string concatenation. PHP <?php // To perform string concatenation function insertChars($str, $insert, $position) { return substr($str, 0, $position) . $insert . substr($str, $position); } // Given Data $str = "Hello World"; $insertStr = "Beautiful "; $position = 6; $newStr = insertChars($str, $insertStr, $position); echo $newStr; ?> OutputHello Beautiful World Time Complexity: O(1)Auxiliary Space: O(1)2. Using substr_replace() FunctionThis function is used for replacing a part of a string with another string, and can also be used for insertion. The substr_replace() function takes 4 arguments: the original string, the string to be inserted, the position for insertion, and the length of the substring to be replaced (0 in this case, as we are only inserting), and return the updated string.Example: Implementation of inserting characters in a string at a certain position using substr_replace() function. PHP <?php // Given Data $str = "Hello World"; $insertStr = "Beautiful "; $position = 6; // Using substr_replace() for string insertion $newStr = substr_replace($str, $insertStr, $position, 0); echo $newStr; ?> OutputHello Beautiful World Time Complexity: O(1)Auxiliary Space: O(1)3. Using mb_substr() FunctionThe mb_substr() function in PHP is used to handle multibyte strings safely. You can utilize this function to split the string into parts, insert the new string, and concatenate the parts back together.Example: In this approach, mb_substr() is used to extract two parts of the original string: one from the start to the insertion position and the other from the insertion position to the end. The new string is then concatenated between these two parts, resulting in the desired output. PHP <?php $str = "Welcome GeeksforGeeks"; $insertStr = "to "; $position = 8; $part1 = mb_substr($str, 0, $position); $part2 = mb_substr($str, $position); $result = $part1 . $insertStr . $part2; echo $result; ?> OutputWelcome to GeeksforGeeksTime Complexity: O(1)Auxiliary Space: O(1)4.Using the str_split() Functionwe are using str_split() Function to insert a string into another string at a specified position is by utilizing the str_split() function. This function splits a string into an array, where each element is a substring of the original string. We can then insert the desired string into the array at the specified position and finally concatenate the array back into a single string.Example: PHP <?php function insertString($str, $insertStr, $position) { // Split the original string into an array $array = str_split($str); // Insert the new string at the desired position array_splice($array, $position, 0, $insertStr); // Join the array back into a single string return implode('', $array); } echo insertString("Welcome GeeksforGeeks", "to ", 8) . PHP_EOL; echo insertString("Hello World", "Beautiful ", 6) . PHP_EOL; ?> Output:Welcome to GeeksforGeeksHello Beautiful World Comment More infoAdvertise with us Next Article PHP Syntax V vkash8574 Follow Improve Article Tags : PHP PHP-string Similar Reads PHP Tutorial PHP is a popular, open-source scripting language mainly used in web development. It runs on the server side and generates dynamic content that is displayed on a web application. 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