douxiuyu2028 2012-01-03 16:52
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C for循环与PHP for循环不同吗?

It seems like the following from the PHP manual regarding for loops is incorrect.

They behave like their C counterparts.

This is my understanding of for loops.
In C
for (i = foo; i < 10; i++) { /* body */ }
is equivalent to

if ( i = foo )  
{   while (i < 10)  
    {    /* body */
         i++;
    }
}

In PHP the comparable loop
for ($i = $foo; $i < 10; $i++) { /* body */ }
becomes

$i = $foo;
while ($i < 10)
{   /* body */
    $i++;
}

The difference is that in PHP $i = $foo is not a condition but rather a convenient place for a statement. Suppose we change the single = to ==. The distinction becomes significant. Is this correct? If so, then PHP and C loops behave differently and the manual is incorrect, right?

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  • doulanyan6455 2012-01-03 16:54
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    They are exactly the same, but your understanding of C's for loops is wrong. They are the same as in PHP.

     for (x; y; z) { /* body */ }
    

    is almost like

     x;
    
     while (y) {
         /* body */
         z;
     }
    

    Though the for and while examples in C are not exactly the same because of scopes and things.

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