PHP Loop Statement Depth Understanding Analysis--while, for, foreach, do While

Loop structure
one, while Loop
while (expression)
{
The loop body;//executes repeatedly until the expression is false
}

Code:
$index = 1;
while ($index <5)
{
Print "number is {$index}
";
$index + +;
}
print "Done";
Operation Result:
Number is 1
Number is 2
Number is 3
Number is 4
Done

second, do and loop
Do {
the loop body;//executes repeatedly until the expression is False
} while (expression)

Code:
Do {
$index + +;
print "number is {$index}
";
} while ($index <0);
print "Done";
Operation Result:
Number is 1
Done

There is a difference between the Do while Loop statement and while, and the difference is that the do and regardless of whether the condition is true will be executed first, while the while must be true to execute once.

Third, for Loop
There are two types of loops depending on the loop condition
One: Count loops (general use for)
Another: Conditional loops (typically using while Do-while)
For (EXPR1; expr2; expr3) {
Statement
 }
where the EXPR1 is the initial value of the condition. EXPR2 is a condition for judging, usually with a logical operation symbol (logical operators)
when judging the conditions. EXPR3 the part to be executed after the execution of the statement, to change the condition for the next cycle judgment, such as add one. Wait a minute. and statement
for a qualifying execution part program, if the program has only one row, you can omit the curly brace {}.
The following example is a "dare not" example written with a for loop, which can be compared with a while loop.
<?php
For ($i =1; $i <=5; $i + +) {
echo "$i. Not anymore.
n ";
 }
?>Operation Result:
1. Not anymore.
2. Not anymore.
3. Not anymore.
4. Not anymore.
5. Not anymore.

Four, foreach Loop

The foreach statement is used to iterate through an array. For Each loop, the value of the current array element is assigned to the value variable (the array pointer moves one at a time)-and so on

Syntax:
foreach (array as value)
{
code to be executed;
}
Code:
<?php
$arr =array ("One", " One", "one", "three");

foreach ($arr as $value)
{
echo "Value:". $value. "
";
}
?>Operation Result:
Value:one
Value:two
Value:three
The above is PHP in four kinds of circulating body, according to different conditions to choose the appropriate circulation body application

PHP Loop Statement Depth Understanding Analysis--while, for, foreach, do While