Commonly used string functions in PHP development

PHP is a widely used server-side scripting language. It has the advantages of being easy to learn, simple, fast to develop, and cross-platform. It has been widely used in website development. Strings are one of the most basic data types in programs and are used to store text information. In PHP development, string operations are very frequent, so it is very important to understand and master string functions.

This article will introduce some commonly used PHP string functions. These functions can be divided into the following categories: string interception functions, string replacement functions, string search functions, string case conversion functions, string encoding functions, string formatting functions, etc.

1. String interception function

Intercepting a string is one of the frequently used string operations. PHP provides a variety of functions for string interception. Here are some commonly used functions:

substr($string, $start[, $length]): intercept a part of the given string. The first parameter is the string to be intercepted, the second parameter is the starting position of interception, and the third parameter is the length of interception (optional parameter). For example:

$str = 'Hello, world!';
$sub = substr($str, 0, 5); // 'Hello'

mb_substr($string, $start[, $length[, $encoding]]): Similar to substr() in function, it can handle multi-byte characters. It should be noted that this function requires mbstring extension support. For example:

$str = '世界，你好！';
$sub = mb_substr($str, 0, 2, 'UTF-8'); // '世界'

2. String replacement function

String replacement is also one of the commonly used string operations. PHP provides a variety of functions for string replacement. Here are some commonly used functions:

str_replace($search, $replace, $string): Replace some parts of the string with other content. The first parameter is the part to be replaced, the second parameter is the replaced content, and the third parameter is the string to be operated on. For example:

$str = 'Today is sunny.';
$newstr = str_replace('sunny', 'rainy', $str); // 'Today is rainy.'

preg_replace($pattern, $replacement, $subject): Replace part of the string with a regular expression. We can use regular expressions to match exactly what we want to replace. For example:

$str = 'The quick brown fox jumps over the lazy dog.';
$newstr = preg_replace('/s+/', '-', $str); // 'The-quick-brown-fox-jumps-over-the-lazy-dog.'

3. String search function

In the PHP development process, it is often necessary to find whether a string contains certain content, or to find whether certain strings contain certain contents in the original string. position in the string. PHP provides a variety of search functions. Here are some commonly used ones:

strpos($haystack, $needle[, $offset]): Find whether the string contains the specified substring and return the first time The location where it appears. If it is not found, it returns FALSE. Note that this function is case-sensitive. For example:

$str = 'The quick brown fox jumps over the lazy dog.';
$pos = strpos($str, 'fox'); // 16

stripos($haystack, $needle[, $offset]): Functionally similar to strpos(), but not case-sensitive. For example:

$str = 'The quick brown fox jumps over the lazy dog.';
$pos = stripos($str, 'FOX'); // 16

4. String case conversion function

In PHP, we often need to convert strings to uppercase or lowercase, or capitalize the first letter. PHP provides the following commonly used functions:

strtolower($string): Convert a string to lowercase. For example:

$str = 'Hello, World!';
$newstr = strtolower($str); // 'hello, world!'

strtoupper($string): Convert the string to uppercase. For example:

$str = 'Hello, World!';
$newstr = strtoupper($str); // 'HELLO, WORLD!'

ucfirst($string): Convert the first letter of the string to uppercase. For example:

$str = 'hello, world!';
$newstr = ucfirst($str); // 'Hello, world!'

5. String encoding function

In PHP, it is often necessary to convert the encoding of strings. According to different business needs, we need to convert the original characters into Methods for converting string encodings to different character sets. PHP provides the following commonly used functions:

mb_convert_encoding($str, $to_encoding[, $from_encoding]): Convert the encoding of a string from one character set to another. The first parameter is the string to be converted, the second parameter is the target encoding, and the third parameter is the source encoding (optional). For example:

$str = '世界，你好！';
$newstr = mb_convert_encoding($str, 'GBK', 'UTF-8'); // '世界，你好！'

6. String formatting function

In PHP development, we often need to format data types such as time and numbers for string formatting and output. PHP provides the following commonly used formatting functions:

date($format[, $timestamp]): Output the current date and time. The first parameter is the date format and the second parameter is an optional timestamp. For example:

$date = date('Y-m-d H:i:s'); // '2022-01-01 12:00:00'

number_format($number[, $decimals[, $dec_point[, $thousands_sep]]]): Format numbers. The first parameter is the number to format, the second parameter is the number of digits after the decimal point (optional parameter), the third parameter is the decimal point symbol (optional parameter), and the fourth parameter is the thousands separator ( optional parameters). For example:

$num = 1234567.89;
$newnum = number_format($num, 2, '.', ','); // '1,234,567.89'

Summary

This article introduces the string functions commonly used in PHP development. Understanding and mastering these functions will improve our string operation efficiency and development efficiency. Of course, there are more string functions that are not introduced in this article, and readers can learn and research further as needed.

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