1: Anonymous functions (can only be used in php5.3.0 or above)
Anonymous functions in php (Anonymous functions) , also called closure function (closures), allows you to specify a function without a name. The most commonly used one is the parameter value of the callback function.
Definition of anonymous function:
$closureFunc = function(){ .... };
eg: Assign the anonymous function to the variable and call it through the variable
$closureFunc = function($str){ echo $str; }; $closureFunc("hello world!");
Output: hello world!
2: Closure
2.1 Put the anonymous function in a normal function, or you can return the anonymous function, which constitutes a simple Closure
function closureFunc1(){ $func = function(){ echo "hello"; }; $func(); } closureFunc1();//输出: hello
2.2 In the anonymous function Reference local variable
function closureFunc2(){ $num = 1; $func = function(){ echo $num; }; $func(); } closureFunc2();//Notice: Undefined variable: num
After the above function is run, a Notice error will be reported, indicating that we Local variables cannot be used in anonymous functions. At this time, a PHP keyword use must be quoted. The code is as follows
function closureFunc2(){ $num = 1; $func = function() use($num){ echo $num; }; $func(); } closureFunc2();//输出: 1
2.3 Return anonymous function
function closureFunc3(){ $num = 1; $func = function() use($num){ echo $num; }; return $func; }$func = closureFunc3(); //函数返回匿名函数$func(); //然后我们在用$func() 调用//输出: 1
2.4 How do we pass parameters to the anonymous function when we return it? In fact, it is the same as passing parameters to a normal function.
function closureFunc4(){ $num = 1; $func = function($str) use($num){ echo $num; echo "\n"; echo $str; }; return $func; }$func = closureFunc4();$func("hello, closure4");//输出: //1 //hello, closure4
2.5 How to use closure to change the variable value referenced by the context?
function closureFunc5(){ $num = 1; $func = function() use($num) { echo "\n"; $num++; echo $num; }; echo "\n"; echo $num; return $func; }$func = closureFunc5();$func();$func();$func();//输出: // 1 // 2 // 2 // 2
Looking at the above input results, it is obvious that the purpose has not been achieved. In fact, just add an & reference symbol.
function closureFunc5(){ $num = 2; $func = function() use(&$num) { echo "\n"; $num++; echo $num; }; echo "\n"; echo $num; return $func; }$func = closureFunc5();$func();$func();$func();//输出: // 2 // 3 // 4 // 5
2.6 Pass anonymous functions as parameters
function callFunc($func){ $func("argv"); } callFunc(function($str){ echo $str; })//输出: // argv
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