To convert variables of one type to another is known as type conversion. There are two types of type conversion:

• Implicit type conversion
• Explicit type conversion

Implicit type conversion  : It automatically converts the data type to another.

Case 1:

Binary arithmetic operator : In this case if one is integer and other is floating-point number, then the first is also evaluated as the float. 

If one is string and other is an integer, Then PHP automatically converts the string to an integer.

Case 2:

Boolean expression and expression operator : Where expression must be evaluated as a boolean, PHP converts the result of the expression to a boolean.

Explicit type conversion : In this different type casting is used for conversion. These are :

• (int) (integer) casts to an integer.
• (float) ,(double) ,(real)  casts to a floating point number
• (string) casts to a text string
• (bool) (boolean) casts to a boolean value
• (array) casts to an array
• (object) casts to an object

Some of the exaples are as below:

Example 1 :

Conversion to Integers

<?php

  echo (int)5.999;
  echo "<br/>";
  echo (int)-7.54321;          // it will round toward zero
  echo "<br/>";
  echo (int)1000000000000;     // too big for an int !!!
  echo "<br/>";

?>

Output:

6
-8
-727379968(depending on your computer setup.)

Example 2 :

Conversions to Floating-Point Numbers


<?php

  $f1 = (float)"+5555";             // float value: 5555.0
  $f2 = (float)"-123";              // -123.0
  $f3 = (float)"123.456";           // 123.456
  $f4 = (float)"1.23456e2";         // 123.456
  $f5 = (float)"1.234e-2";          // 0.001234
  $f6 = (float)"1000000000000";     // 1e12 (one trillion)

?>

Example 3: 

Conversion to Booleans


<?php

  $b1 = (bool)0;                 // FALSE
  $b2 = (bool)0.0;               // FALSE
  $b4 = (bool)-10;               // TRUE
  $b5 = (bool)123123e-34;        // TRUE
  $b3 = (bool)(0.4 + 0.2  0.6); // TRUE  not EXACTLY 0.0 ...

?>