Type casting syntax in PHP - Step-by-Step Execution

Concept Flow - Type casting syntax

Start with a variable

↓

Apply type cast syntax

↓

Variable changes type

↓

Use the new typed variable

↓

End

This flow shows how a variable is changed from one type to another using PHP's type casting syntax.

Execution Sample

PHP

<?php
$var = "123";
$intVar = (int)$var;
echo $intVar;
?>

This code converts a string containing digits into an integer and prints it.

Execution Table

Step	Action	Variable	Value Before	Type Before	Value After	Type After	Output
1	Initialize variable	$var	undefined	undefined	"123"	string
2	Apply (int) cast	$intVar	undefined	undefined	123	integer
3	Print $intVar	$intVar	123	integer	123	integer	123
4	End	-	-	-	-	-	-

💡 Execution stops after printing the integer value 123.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	Final
$var	undefined	"123"	"123"	"123"	"123"
$intVar	undefined	undefined	123	123	123

Key Moments - 2 Insights

Why does (int)$var change the type but not the original $var?

Because (int)$var creates a new value with integer type assigned to $intVar, but $var remains the original string as shown in execution_table step 2 and variable_tracker.

What happens if the string contains letters, like "123abc"?

PHP converts the initial numeric part to integer and stops at the first non-digit, so (int)"123abc" becomes 123. This is consistent with PHP's casting rules.

Visual Quiz - 3 Questions

Look at the execution_table at step 2, what is the type of $intVar after casting?

A integer

B float

C string

D boolean

💡 Hint

Check the 'Type After' column for $intVar at step 2 in execution_table.

At which step is the output produced?

A Step 1

B Step 3

C Step 2

D Step 4

💡 Hint

Look at the 'Output' column in execution_table to find when output appears.

If $var was "45.67" and cast to (int), what would $intVar be?

A 45.67

B 46

C 45

D "45.67"

💡 Hint

Casting float-like strings to int truncates the decimal part, as per PHP casting rules.

Concept Snapshot

PHP Type Casting Syntax:
- Use (type) before a variable to convert it.
- Common types: (int), (float), (string), (bool), (array), (object).
- Casting creates a new value; original variable unchanged.
- Example: $intVar = (int)$var;
- Useful to ensure variable is the expected type.

Full Transcript

This lesson shows how PHP changes a variable's type using type casting syntax. We start with a string variable $var holding "123". Then we create a new variable $intVar by casting $var to integer using (int)$var. This changes the value to 123 as an integer type. When we print $intVar, the output is 123. The original $var remains a string. This process helps convert data types explicitly in PHP. The execution table traces each step, showing variable values and types before and after casting. Key points include that casting creates a new typed value without changing the original variable, and that PHP converts strings with numbers correctly to integers. The quiz checks understanding of types after casting, output timing, and casting behavior with float-like strings.