PHP strlen() Function

How to Find String Length in PHP?

The strlen() function in PHP is specifically designed to measure the length of a string. By passing a string as an argument to this function, we can quickly obtain the count of characters contained within the string.

The strlen() function works by scanning the entire string, character by character until it finds the null character (which marks the end of the string). This means that if the string is very long, the strlen() function will have to scan a lot of memory. In memory-restricted environments, such as embedded systems, this can be a problem.

Incremental reading and buffering are two techniques that can be used to avoid this problem. Incremental reading involves reading the string one character at a time, and buffering involves storing the string in a buffer so that it can be read more efficiently. Both of these techniques can help to reduce the amount of memory that is used by the strlen() function.

PHP strlen() Function: Syntax

The syntax of the strlen() function is quite simple:

PHP strlen() Function: Parameters

The strlen() function takes a single mandatory parameter:

• $string: This parameter is mandatory and should be the string for which we want to determine the length.

PHP strlen() Function: Return Value

The function returns an integer value representing the length of the given string.

Examples of PHP strlen() Function

Let's take a look at some practical examples to understand how the strlen() function works.

Example - 1: Return the Length of the String "Hello World"

Output:

Explanation:

In this example, the string "Hello World" consists of 11 characters, which includes the space between "Hello" and "World." As a result, the strlen() function correctly yields a value of 11.

Example - 2: Using strlen() Function with a String Containing Special Characters

Output:

Explanation:

In the above example, we are using the strlen() function to calculate the length of the string "Héllo, Wørld!". This string contains various special characters and symbols, such as the accented letters "é" and "ø".

When determining the length of a string using strlen(), it counts the number of bytes used to represent the string, not the number of visible characters. In many cases, each character is encoded using multiple bytes, especially when dealing with non-ASCII characters or special symbols.

Multibyte character encodings, such as UTF-8, use multiple bytes to represent each character. This is done to accommodate a wider range of characters, including those from non-Latin scripts and emojis. The number of bytes used to represent each character depends on the character itself. For example, an ASCII character is represented by a single byte, while a Chinese character may be represented by two or three bytes.

When the strlen() function is used on a string that contains multiple characters, it will count the number of bytes in the string, not the number of characters. This means that the strlen() result will be greater than the number of characters in the string if it contains any multibyte characters.

In the case of "Héllo, Wørld!", the string is encoded using the UTF-8 character encoding. The accented characters "é" and "ø" are represented by multiple bytes each in UTF-8. Therefore, even though the string appears to have 13 visible characters, it consists of 15 bytes.

Example - 3: Handling Numeric Strings

Output:

Explanation:

In this example, the strlen() function showcases its versatility in evaluating numeric strings. The string "12345" might consist solely of digits, but strlen() treats each digit as an individual character. Consequently, the length of the numeric string is correctly determined to be 5, demonstrating that strlen() isn't limited to textual content but also handles numeric sequences.

Example - 4: Empty String Scenario

Output:

Explanation:

Even though an empty string appears devoid of any visible characters, it's far from insignificant. This example highlights the precision of the strlen() function, which accurately identifies the length of an empty string as 0. This showcases that strlen() doesn't overlook even the absence of characters, ensuring consistent and dependable behavior when dealing with varying types of strings.

Alternative to strlen() Function

The strlen() function operates on bytes, not characters. This means that the number of bytes in a string may not be the same as the number of characters in the string, depending on the character encoding.

Multibyte-safe functions are designed to work with strings that are encoded in multibyte encodings. They will correctly count the number of characters in the string, regardless of the character encoding.

The mb_strlen() function is such an alternative to the strlen() function that can be used to get the number of characters in a string, regardless of the character encoding. The mb_strlen() function takes two arguments: the string and the character encoding. The default character encoding is UTF-8.

Example

Output:

Explanation:

In this example, the mb_strlen() function will return the value 6, which is the number of characters in the string, not the number of bytes. On the other hand, the strlen function is returning 8 in this case.