Random tip that works well across several languages.

Turn that test around. If you write it:

if (5 == $number) {
  # ...
}
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then you are automatically told your mistake when you write

if (5 = $number) {
  # ...
}
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by accident. By contrast you are rather less happy if you write in the naive order and wound up with:

if ($number = 5) {
  # ...
}
[download]

which winds up being true rather more often than you would like...