Top 10 commonly used functions in PHP

As a programming language widely used in Web development, PHP has a rich function library, including some commonly used functions. In this article, we will introduce you to the TOP10 commonly used functions in PHP and explain their uses and basic usage.

1. strlen() function

strlen() function is used to calculate the length of a string, that is, the number of characters. Its syntax format is as follows:

strlen(string $string) : int

Among them, the $string parameter is the string whose length needs to be calculated. This function returns an integer representing the length of the string.

For example, the output result of the following code is 13, which is the length of the string "Hello, world!":

$string = "Hello, world!";
echo strlen($string);

2. substr() function

The substr() function is used to intercept a substring from a string. Its syntax format is as follows:

substr(string $string , int $start [, int $length ]) : string

Among them, the $string parameter is the string to be intercepted, the $start parameter is the starting position of interception, and the $length parameter is the length of interception (optional, if not specified) Truncated to the end of the string by default).

For example, the output result of the following code is "world", which is the substring intercepted from the string "Hello, world!":

$string = "Hello, world!";
echo substr($string, 7);

3. str_replace() function

str_replace() function is used to replace the specified character or string in a string. Its syntax format is as follows:

str_replace(mixed $search , mixed $replace , mixed $subject [, int &$count ]) : mixed

Among them, the $search parameter is the character or string that needs to be replaced, the $replace parameter is the character or string that needs to be replaced, the $subject parameter is the original string that needs to be replaced, $ The count parameter is optional and indicates the number of replacements (the default is all replacements).

For example, the following code output is "My name is Tom", that is, replace "Tim" in the string "I am Tim" with "Tom":

$string = "I am Tim";
echo str_replace("Tim", "Tom", $string);

4. strtolower ()Function

strtolower() function is used to convert a string to lowercase. Its syntax format is as follows:

strtolower(string $string) : string

Among them, the $string parameter is the string to be converted. This function returns a new string in which all letters are lowercase.

For example, the following code outputs "hello, world!", that is, converts the string "Hello, World!" to lowercase:

$string = "Hello, World!";
echo strtolower($string);

5. strtoupper() function

The strtoupper() function is used to convert a string to uppercase. Its syntax format is as follows:

strtoupper(string $string) : string

Among them, the $string parameter is the string to be converted. This function returns a new string in which all letters are uppercase.

For example, the output result of the following code is "HELLO, WORLD!", which converts the string "Hello, World!" to uppercase:

$string = "Hello, World!";
echo strtoupper($string);

6. trim() function

trim() function is used to remove spaces or specified characters on both sides of a string. Its syntax format is as follows:

trim(string $string [, string $characters ]) : string

Among them, the $string parameter is the string to be operated on, and the $characters parameter is optional, indicating the characters to be removed (default is space).

For example, the output result of the following code is "hello", that is, the spaces on both sides of the string "hello" are removed:

$string = "  hello  ";
echo trim($string);

7. explode() function

explode() function is used to split a string into an array according to the specified delimiter. Its syntax format is as follows:

explode(string $delimiter , string $string [, int $limit = PHP_INT_MAX ]) : array

Among them, the $delimiter parameter is the delimiter, the $string parameter is the string to be split, and the $limit parameter is optional, indicating that the maximum length of the output array is limited (the default is unlimited ).

For example, the output result of the following code is

array(3) {
  [0]=>
  string(5) "apple"
  [1]=>
  string(6) "banana"
  [2]=>
  string(5) "grape"
}

The string "apple,banana,grape" is divided into arrays according to ",":

$string = "apple,banana,grape";
$array = explode(",", $string);
print_r($array);

8. implode( )Function

implode() function is used to concatenate an array into a string according to the specified connector. Its syntax format is as follows:

implode(string $glue , array $pieces) : string

Among them, the $glue parameter is the connector, and the $pieces parameter is the array to be connected.

For example, the output result of the following code is "apple|banana|grape", which is a string formed by concatenating the array [apple, banana, grape] with "|":

$array = array("apple", "banana", "grape");
$string = implode("|", $array);
echo $string;

9. include() function

include() function is used to introduce a file into the current script. Its syntax is as follows:

include(string $filename) : mixed

Among them, the $filename parameter is the name of the file to be imported. This function returns a value that represents the value returned by the last statement executed by the imported file; if the file does not exist, it returns false.

For example, the following code will import a file named "example.php":

include("example.php");

10. date() function

date() function uses To get the current date and time. Its syntax is as follows:

date(string $format [, int $timestamp = time() ]) : string

Among them, the $format parameter is the date and time format string, and the $timestamp parameter is optional, indicating the input timestamp (the default is the current time).

For example, the following code outputs the current date and time in the format "Y-m-d H:i:s":

$dateString = date('Y-m-d H:i:s');
echo $dateString;

The above is an introduction to the TOP10 commonly used functions in PHP. I hope these functions can help You shorten development time and improve development efficiency. Of course, the PHP function library is much more than these, welcome to continue learning and discuss in depth!

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