This article mainly summarizes some useful little knowledge in PHP that is found in daily work but is easily ignored by people, such as whether the PHP function determines whether the function exists, the variable function of the PHP function, etc. Friends who need it, please follow the editor to take a look at the detailed introduction.
This article mainly summarizes some useful knowledge in PHP and shares it for your reference and learning. Let’s take a look at the detailed introduction:
1. PHP functions Determine whether the function exists
When we create a custom function and understand the usage of variable functions, in order to ensure that the function called by the program exists, we often use function_exists to determine whether the function exists. . The same method_exists can be used to detect whether a class method exists.
function func() {
}
if (function_exists('func')){
echo 'exists';
} Whether the class is defined can use class_exists
class MyClass{
}
// 使用前检查类是否存在
if (class_exists('MyClass')) {
$myclass = new MyClass();
}There is in PHP There are many such checking methods, such as whether the file exists file_exists, etc.
$filename = 'test.txt';
if (!file_exists($filename)) {
echo $filename . ' not exists.';
}##2. Variable functions of PHP functions
The so-called variable function refers to calling a function through the value of a variable. Because the value of a variable is variable, different functions can be called by changing the value of a variable. It is often used in callback functions, function lists, or to call different functions based on dynamic parameters. The method of calling a variable function is to add parentheses to the variable name.function name() {
echo 'jobs';
}
$func = 'name';
$func(); //调用可变函数class book {
function getName() {
return 'bookname';
}
}
$func = 'getName';
$book = new book();
$book->$func();$func = 'getSpeed'; $className = 'Car'; echo $className::$func(); //动态调用静态方法
class Car {
private static $speed = 10;
public static function getSpeed() {
return self::$speed;
}
public static function speedUp() {
return self::$speed+=10;
}
}
class BigCar extends Car {
public static function start() {
parent::speedUp();
}
}
BigCar::start();
echo BigCar::getSpeed();3. Advanced features of PHP classes and objects
Object comparison, when the same class When all attributes of two instances are equal, you can use the comparison operator == to judge. When you need to judge whether two variables are references to the same object, you can use the congruence operator === to judge.class Car {
}
$a = new Car();
$b = new Car();
if ($a == $b) echo '=='; //true
if ($a === $b) echo '==='; //falseclass Car {
public $name = 'car';
public function __clone() {
$obj = new Car();
$obj->name = $this->name;
}
}
$a = new Car();
$a->name = 'new car';
$b = clone $a;
var_dump($b);class Car {
public $name = 'car';
}
$a = new Car();
$str = serialize($a); //对象序列化成字符串
echo $str.'<br>';
$b = unserialize($str); //反序列化为对象
var_dump($b);4. Get the length of the string in PHP string
There is a magical function in php, You can directly get the length of the string. This function is strlen().$str = 'hello'; $len = strlen($str); echo $len;//输出结果是5
$str = "我爱你"; echo mb_strlen($str,"UTF8");//结果：3，此处的UTF8表示中文编码是UTF8格式，中文一般采用UTF8编码
5. PHP string formatting string
If there is a string $str = ' 99.9';, how to make this string become 99.90? We need to use PHP's formatted string function sprintf()Function description: sprintf (format, string to be converted)Return: Formatted The string$str = '99.9'; $result = sprintf('%01.2f', $str); echo $result;//结果显示99.90
6. PHP string escaping
php string escape functionaddslashes()
返回值：一个经过转义后的字符串
$str = "what's your name?"; echo addslashes($str);//输出：what\'s your name?
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