Usage of for(), while(), and foreach() in loops in php_PHP tutorial
WBOYOriginal
2016-07-13 17:13:01896browse
This article introduces the use of the most basic loop statements, including the most basic statements such as for(), while(), foreach() do while in php.
while loop
The while loop is the simplest loop in PHP, its basic format is:
The code is as follows
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while (expr){
代码如下
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while (expr){
statement
}
//或者
while (expr):
statement
endwhile;
Statement
}
//or
while (expr):
Statement
代码如下
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$i = 1;
while ($i <= 10) {
echo $i;
$i++;
}
?>
endwhile;
This syntax means that as long as the expr expression is TRUE, the statement will be executed until expr is FALSE. The statement represents the action or logic to be executed.
Example:
The code is as follows
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$i = 1;
while ($i <= 10) {
代码如下
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do {
statement
}while (expr)
echo $i;
$i++;
}
代码如下
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$i = 1;
do {
echo $i;
$i++;
} while ($i <= 10);
?>
?>
This example loops out 1 to 10.
do-while loop
The do-while loop is very similar to the while loop, the only difference is that do-while is guaranteed to be executed once, while while may not do anything when the expression does not hold.
代码如下
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for (expr1; expr2; expr3){
statement
}
The do-while loop has only one syntax:
The code is as follows
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do {
代码如下
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for ($i = 1; $i <= 10; $i++) {
echo $i;
}
?>
statement
}while (expr)
Example:
The code is as follows
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$i = 1;<🎜>
do {<🎜>
echo $i;<🎜>
$i++;<🎜>
} while ($i <= 10);<🎜>
?>
This example also outputs 1 to 10
for loop
The for loop is a more complex loop in PHP. Its syntax is as follows:
Grammar interpretation
The first expression (expr1) is evaluated unconditionally once before the loop starts
expr2 is evaluated before each loop starts. If the value is TRUE, the loop continues and the nested loop statement is executed; if the value is FALSE, the loop is terminated.
expr3 is evaluated (executed) after each loop
Every expression can be null. If expr2 is empty, the loop will continue indefinitely, but the loop can be ended by break:
The code is as follows
代码如下
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for ($i = 1; ; $i++) {
if ($i > 10) {
break;
}
echo $i;
}
?>
Copy code
for ($i = 1; ; $i++ ) {
If ($i > 10) {
break;
}
echo $i;
}
?>
Tips
When using loop statements, we usually have to be careful not to loop endlessly and cause the program to "zombie". In addition, we must also pay attention to the loop conditions (loop judgment expressions) to ensure that the loop results are correct.
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