for

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# `for`

`for` loops are the most complex loops in PHP. They behave like their C counterparts. The syntax of a `for` loop is:

    for (expr1; expr2; expr3) statement

The first expression (`expr1`) is evaluated (executed) once unconditionally at the beginning of the loop.

In the beginning of each iteration, `expr2` is evaluated. If it evaluates to `TRUE`, the loop continues and the nested statement(s) are executed. If it evaluates to `FALSE`, the execution of the loop ends.

At the end of each iteration, `expr3` is evaluated (executed).

Each of the expressions can be empty. `expr2` being empty means the loop should be run indefinitely (PHP implicitly considers it as `TRUE`, like C). This may not be as useless as you might think, since often you'd want to end the loop using a conditional `break` statement instead of using the `for` truth expression.

Consider the following examples. All of them display numbers from 1 to 10:

    /* example 1 */

    for ($i = 1; $i <= 10; $i++) {
        print $i;
    }

    /* example 2 */

    for ($i = 1;;$i++) {
        if ($i > 10) {
            break;
        }
        print $i;
    }

    /* example 3 */

    $i = 1;
    for (;;) {
        if ($i > 10) {
            break;
        }
        print $i;
        $i++;
    }

    /* example 4 */

    for ($i = 1; $i <= 10; print $i, $i++);

Of course, the first example appears to be the nicest one (or perhaps the fourth), but you may find that being able to use empty expressions in `for` loops comes in handy in many occasions.

PHP also supports the alternate "colon syntax" for `for` loops.

    for (expr1; expr2; expr3): statement; ...; endfor;

Other languages have a `foreach` statement to traverse an array or hash. PHP 3 has no such construct; PHP 4 does (see foreach). In PHP 3, you can combine while with the list() and each() functions to achieve the same effect. See the documentation for these functions for an example.

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