Translations:Manual:Coding conventions/PHP/219/en

Code using single quotes is less error-prone and easier to review, as it can not accidentally contain [$escapes escape sequences] or [$variables variables]. For example, the regular expression $regex1 requires an extra backslash, making it slightly more confusing and error-prone than $regex2. Also for people using US/UK qwerty keyboards, they are easier to type, since it avoids the need to press shift.