PHP: Making Statements

Table of Contents:

• 1.Conditional Statements
• 2.PHP Looping

PHP Conditional Statements

Conditional statements in PHP are used to perform different actions based on different conditions.

Conditional Statements

Very often when you write code, you want to perform different actions for different decisions. You can use conditional statements in your code to do this.

In PHP we have two conditional statements:

• if (...else) statement - use this statement if you want to execute a set of code when a condition is true (and another if the condition is not true)
• switch statement - use this statement if you want to select one of many sets of lines to execute

The If Statement

If you want to execute some code if a condition is true and another code if a condition is false, use the if....else statement.

Syntax

if (condition)
code to be executed if condition is true;
else
code to be executed if condition is false;

Example

The following example will output "Have a nice weekend!" if the current day is Friday, otherwise it will output "Have a nice day!":

$d=date("D");
if ($d=="Fri")
echo "Have a nice weekend!"; 
else
echo "Have a nice day!"; 
?>

If more than one line should be executed when a condition is true, the lines should be enclosed within curly braces:

$x=10;
if ($x==10)
{
echo "Hello
"; 
echo "Good morning
";
}
?>

The Switch Statement

If you want to select one of many blocks of code to be executed, use the Switch statement.

Syntax

switch (expression)
{
case label1:
  code to be executed if expression = label1;
  break;  
case label2:
  code to be executed if expression = label2;
  break;
default:
  code to be executed
  if expression is different 
  from both label1 and label2;
}

Example

This is how it works: First we have a single expression (most often a variable), that is evaluated once. The value of the expression is then compared with the values for each case in the structure. If there is a match, the block of code associated with that case is executed. Use break to prevent the code from running into the next case automatically. The default statement is used if none of the cases are true.

switch ($x)
{
case 1:
  echo "Number 1";
  break;
case 2:
  echo "Number 2";
  break;
case 3:
  echo "Number 3";
  break;
default:
  echo "No number between 1 and 3";
}
?>

PHP Looping

Looping statements in PHP are used to execute the same block of code a specified number of times.

Looping

Very often when you write code, you want the same block of code to run a number of times. You can use looping statements in your code to perform this.

In PHP we have the following looping statements:

• while - loops through a block of code if and as long as a specified condition is true
• do...while - loops through a block of code once, and then repeats the loop as long as a special condition is true
• for - loops through a block of code a specified number of times
• foreach - loops through a block of code for each element in an array

The while Statement

The while statement will execute a block of code if and as long as a condition is true.

Syntax

while (condition)
code to be executed;

Example

The following example demonstrates a loop that will continue to run as long as the variable i is less than, or equal to 5. i will increase by 1 each time the loop runs:

$i=1;
while($i<=5)
{
echo "The number is " . $i . "
";
$i++;
}
?>

The do...while Statement

The do...while statement will execute a block of code at least once - it then will repeat the loop as long as a condition is true.

Syntax

do
{
code to be executed;
}
while (condition);

Example

The following example will increment the value of i at least once, and it will continue incrementing the variable i while it has a value of less than 5:

$i=0;
do
{
$i++;
echo "The number is " . $i . "
";
}
while ($i<5);
?>

The for Statement

The for statement is used when you know how many times you want to execute a statement or a list of statements.

Syntax

for (initialization; condition; increment)
{
    code to be executed;
}

Note: The for statement has three parameters. The first parameter is for initializing variables, the second parameter holds the condition, and the third parameter contains any increments required to implement the loop. If more than one variable is included in either the initialization or the increment section, then they should be separated by commas. The condition must evaluate to true or false.

Example

The following example prints the text "Hello World!" five times:

for ($i=1; $i<=5; $i++)
{
echo "Hello World!
";
}
?>

The foreach Statement

Loops over the array given by the parameter. On each loop, the value of the current element is assigned to $value and the array pointer is advanced by one - so on the next loop, you\\\\'ll be looking at the next element.

Syntax

foreach (array as value)
{
    code to be executed;
}

Example

The following example demonstrates a loop that will print the values of the given array:

$arr=array("one", "two", "three");
foreach ($arr as $value)
{
echo "Value: " . $value . "
";
}
?>