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Open Source Technologies

Notes PHP provides C-style for loops. The for loop accepts three arguments: for (start_expressions;
truth_expressions; increment_expressions). Most commonly, for loops are used with only one
expression for each of the start, truth, and increment expressions, which would make the previous
syntax table look slightly more familiar.

Statement Statement List
for (expr; expr; expr) for (expr; expr; expr):
statement statement list endfor;

The start expression is evaluated only once when the loop is reached. Usually it is used to
initialize the loop control variable. The truth expression I evaluated in the beginning of every
loop iteration. If true, the statements inside the loop will be executed; if false, the loop ends.
The increment expression is evaluated at the end of every iteration before the truth expression
is evaluated. Usually, it is used to increment the loop control variable, but it can be used for
any other purpose as well. Both break and continue behave the same way as they do with while
loops. continue causes evaluation of the increment expression before it re-evaluates the truth
expression.

Example: for ($i = 0; $i < 10; $i++) {
print “The square of $i is “ . $i*$i . “\n”;

}

The result of running this code is
The square of 0 is 0

The square of 1 is 1
...

The square of 9 is 81

Like in C, it is possible to supply more than one expression for each of the three arguments
by using commas to delimit them. The value of each argument is the value of the rightmost
expression. Alternatively, it is also possible not to supply an expression with one or more of
the arguments. The value of such an empty argument will be true. For example, the following
is an infinite loop:
for (; ;) {

print “I’m infinite\n”;

}
Infinite loops are, as the name suggests, loops that run without bounds. If your
loop is running infinitely, your script is running for an infinite amount of time.
This is very stressful on your Web server, and renders the Web page unusable.

Make the syntax table.

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