Introduction to PHP built-in functions

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Release: 2024-04-19 18:39:02
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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)

PHP 内置函数介绍

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"
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  • strtoupper(): Convert a string to uppercase.
$string = "Hello World";
$stringToUpper = strtoupper($string); // 结果为 "HELLO WORLD"
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  • strtolower(): Convert the string to lowercase.
$string = "HELLO WORLD";
$stringToLower = strtolower($string); // 结果为 "hello world"
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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]
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  • 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]
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  • 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"
}
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Mathematical functions

  • round(): Rounds a number to the specified decimal places.
$number = 3.14159;
$roundedNumber = round($number, 2); // 结果为 3.14
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  • abs(): Returns the absolute value of the number.
$number = -5;
$absoluteNumber = abs($number); // 结果为 5
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  • max(): Returns the largest number in a set of numbers.
$numbers = [1, 3, 5, 7, 9];
$maxNumber = max($numbers); // 结果为 9
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File function

  • fopen(): Open the file and return the file handle.
$handle = fopen("myfile.txt", "r"); // 读模式打开 myfile.txt
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  • fread(): Read data from the file handle.
$data = fread($handle, 100); // 从 myfile.txt 中读取前 100 个字节
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  • fclose(): Close the file handle.
fclose($handle); // 关闭 myfile.txt 文件句柄
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