Introduction to PHP built-in functions

PHP provides a series of built-in functions for performing various tasks, including: string operations (strcmp, strtoupper, strtolower) array processing (array_push, array_pop, in_array) mathematical operations (round, abs, max) file processing ( fopen, fread, fclose)

Introduction to PHP built-in functions

PHP built-in functions are a set of functions predefined in PHP , which provide convenient methods for handling a variety of tasks, such as string manipulation, array manipulation, mathematical operations, and file processing. This article will introduce some commonly used built-in functions and demonstrate their usage through practical cases.

String function

• strcmp(): Compares two strings. Returns 0 for same, < 0 for first string less than second string, > 0 for first string greater than second string.

$result = strcmp("Hello", "World"); // 结果为 -1，"Hello" 小于 "World"

• strtoupper(): Convert a string to uppercase.

$string = "Hello World";
$stringToUpper = strtoupper($string); // 结果为 "HELLO WORLD"

• strtolower(): Convert the string to lowercase.

$string = "HELLO WORLD";
$stringToLower = strtolower($string); // 结果为 "hello world"

Array function

• array_push(): Append elements to the end of the array.

$array = [1, 2, 3];
array_push($array, 4); // 结果为 [1, 2, 3, 4]

• array_pop(): Removes and returns the last element from the end of the array.

$array = [1, 2, 3, 4];
$lastElement = array_pop($array); // 结果为 4，数组变为 [1, 2, 3]

• in_array(): Check whether an element exists in the array.

$array = [1, 2, 3, 4];
if (in_array(2, $array)) {
  echo "2 exists in the array"; // 输出 "2 exists in the array"
}

Mathematical functions

• round(): Rounds a number to the specified decimal places.

$number = 3.14159;
$roundedNumber = round($number, 2); // 结果为 3.14

• abs(): Returns the absolute value of the number.

$number = -5;
$absoluteNumber = abs($number); // 结果为 5

• max(): Returns the largest number in a set of numbers.

$numbers = [1, 3, 5, 7, 9];
$maxNumber = max($numbers); // 结果为 9

File function

• fopen(): Open the file and return the file handle.

$handle = fopen("myfile.txt", "r"); // 读模式打开 myfile.txt

• fread(): Read data from the file handle.

$data = fread($handle, 100); // 从 myfile.txt 中读取前 100 个字节

• fclose(): Close the file handle.

fclose($handle); // 关闭 myfile.txt 文件句柄

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