Common validation patterns in PHP - Step-by-Step Execution

Concept Flow - Common validation patterns

Start Input

↓

Check if empty?

Yes→Error: 'Input required'

No↓

Check format (e.g. email)?

No→Error: 'Invalid format'

Yes↓

Check length?

No→Error: 'Invalid length'

Yes↓

Validation Passed

↓

End

Input goes through checks: empty, format, length. If any fail, error shown. Otherwise, validation passes.

Execution Sample

PHP

<?php
$input = "[e-mail]";
if (empty($input)) {
  echo "Error: Input required";
} elseif (!filter_var($input, FILTER_VALIDATE_EMAIL)) {
  echo "Error: Invalid format";
} elseif (strlen($input) > 50) {
  echo "Error: Invalid length";
} else {
  echo "Validation Passed";
}
?>

Checks if input is empty, then if it's a valid email, then if length is acceptable, printing error or success.

Execution Table

Step	Condition Checked	Condition Result	Branch Taken	Output
1	empty($input)	False	No error, continue
2	!filter_var($input, FILTER_VALIDATE_EMAIL)	False	No error, continue
3	strlen($input) > 50	False	No error, continue
4	All checks passed	True	Print success	Validation Passed

💡 All conditions passed, so validation succeeds and 'Validation Passed' is printed.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	Final
$input	"[e-mail]"	"[e-mail]"	"[e-mail]"	"[e-mail]"	"[e-mail]"

Key Moments - 3 Insights

Why does the code check empty($input) first?

Because if input is empty, no need to check format or length. The execution_table row 1 shows it stops early if empty.

What happens if the email format is wrong?

The code prints 'Error: Invalid format' and stops. See execution_table row 2 where the condition would be True and branch taken.

Why check length after format?

Because format check is more important first; length check only matters if format is valid. Execution_table rows 2 and 3 show this order.

Visual Quiz - 3 Questions

Look at the execution_table, what is the output if $input is empty?

A Error: Invalid format

B Error: Input required

C Error: Invalid length

D Validation Passed

💡 Hint

Check execution_table row 1 where empty($input) condition is True and error is printed.

At which step does the code check if the input is a valid email?

A Step 1

B Step 3

C Step 2

D Step 4

💡 Hint

See execution_table column 'Condition Checked' for step 2.

If the input length was 60 characters, what would happen at step 3?

A Condition true, print 'Error: Invalid length'

B Condition true, print 'Error: Invalid format'

C Condition false, continue

D Validation Passed

💡 Hint

Look at execution_table row 3 condition about length and what happens if true.

Concept Snapshot

Common validation pattern in PHP:
1. Check if input is empty with empty().
2. Check format using filter_var() for emails.
3. Check length with strlen().
Print error on first failure, else success.
Order matters for efficiency and clarity.

Full Transcript

This example shows common validation steps in PHP. First, the input is checked if empty using empty(). If empty, an error message is printed and validation stops. If not empty, the input is checked for valid email format using filter_var() with FILTER_VALIDATE_EMAIL. If the format is invalid, an error message is printed. Next, the input length is checked with strlen() to ensure it is not too long. If length is too long, an error message is printed. If all checks pass, the code prints 'Validation Passed'. The execution table shows each step's condition, result, branch taken, and output. The variable tracker shows the input value remains the same throughout. Key moments clarify why the order of checks matters and what happens on failures. The visual quiz tests understanding of the steps and outputs. This pattern helps catch common input errors clearly and efficiently.