Issues caused by using references in foreach

Don't say much nonsense, just look at the following code:

$arrarray('a','b','c','d');     foreach($arras &$v){}     foreach($arras$v){          var_dump($v);     }

After running, the results are as follows:

string'a' (length=1)string'b' (length=1)string'c' (length=1)string'c' (length=1)     //这里为什么是c呢？

We wonder why the last one is C and not d?

In fact, the reason is very simple, at the end of the first cycle, the variable v becomes a reference to arr[3]. So, when using foreach for the second time, it is the way to pass the value, which is actually to iterate over the value of the variable arr, then assign the value to the variable V, since the variable v is a reference to arr[3], so assigning the value to the variable v is actually assigned to ARR[3].

Let's Change the code:

$arrarray('a','b','c','d');     foreach($arras &$v){}     foreach($arras$v){          var_dump($arr);//这里把变量$arr打印出来     }

After running, you will find:

Array (size=4)0=string' A '(length=1)1=string' B '(length=1)2=string' C '(length=1)3= &string' A '(length=1) Array (size=4)0=string' A '(length=1)1=string' B '(length=1)2=string' C '(length=1)3= &string' B '(length=1) Array (size=4)0=string' A '(length=1)1=string' B '(length=1)2=string' C '(length=1)3= &string' C '(length=1) Array (size=4)0=string' A '(length=1)1=string' B '(length=1)2=string' C '(length=1)3= &string' C '(length=1)

It can be found that the value of arr[3] has been changing.

'). addclass (' pre-numbering '). Hide (); $ (this). addclass (' has-numbering '). Parent (). append ($numbering); for (i = 1; i <= lines; i++) {$numbering. Append ($ ('

'). Text (i)); }; $numbering. FadeIn (1700); }); });

Copyright NOTICE: This article is the original blogger articles, reproduced please indicate the source.

The above describes the use of references in foreach problems, including aspects of the content, I hope to be interested in PHP tutorial friends helpful.

