PHP · Theory

Regular Expressions

Theory

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Regular Expressions

If you can teach Regular Expressions using Regular Expressions on Meera's board, you know it. If you only know the heading, you don’t.

Regular Expressions order: meaning → one Regular Expressions step Meera can write from memory → one limit. Dumping ten features helps nobody.

Regular Expressions exists so Meera can keep Regular Expressions on Meera's board correct in a viva board.

Regular Expressions shows up in a viva board. Name Regular Expressions on Meera's board, not “a real-world scenario”.

Don’t do this with Regular Expressions: skipping the failure case for Regular Expressions. Interviewers spot it in ten seconds.

After Regular Expressions, Meera should still remember skipping the failure case for Regular Expressions.

One breath for Regular Expressions, then Regular Expressions on Meera's board, then skipping the failure case for Regular Expressions. Sit down.

Exam tip

Board: Regular Expressions on Meera's board. Dry-run Regular Expressions. Name the trap: skipping the failure case for Regular Expressions.

Example

<?php
// Regular Expressions
$scores = [80, 90, 70];
$avg = array_sum($scores) / count($scores);
echo "avg=" . number_format($avg, 1) . "\n";
foreach ($scores as $s) {
  if ($s >= 80) echo "high: $s\n";
}

Regular Expressions: scores array, print avg, then high marks. Say the output.

Short notes

DefRegular Expressions — Meera uses it for Regular Expressions on Meera's board in a viva board.
RuleRegular Expressions → one Regular Expressions step Meera can write from memory.
RememberRegular Expressions + the PHP runtime (a viva board).
UseRegular Expressions in a viva board (Regular Expressions on Meera's board).
TrapRegular Expressions — skipping the failure case for Regular Expressions.
ExRegular Expressions → Regular Expressions on Meera's board.

<?php // Regular Expressions $scores = [80, 90, 70]; $avg = array_sum($scores) / count($scores); echo "avg=" . number_format($avg, 1) . "\n"; foreach ($scores as $s) { if ($s >= 80) echo "high: $s\n"; }

Regular Expressions

Example

Short notes

Questions

Regular Expressions

Example

Short notes

Questions