What are the most common PHP
validation functions and techniques?

• The "ctype" functions

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  • ctype = character type
  • ctype_alpha(), ctype_digit(), ctype_alnum()
  • Very fast

• stripos()

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  • Finds position of a string in a string
  • Return value of 0 = 1st position
  • Returns FALSE if not found
  • Very fast
  • Has problems with multi-byte strings
  • Use strpos() for case sensitive

• preg_match()

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  • Intelligent match using a regular expression
  • Use "u" modifier to support UTF-8
  • Performance considerations involved
  • Do not use in a lengthy loop

• Validation by lookup

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  • Often associated with HTML <select> tags
  • Validate against a list of known values
  • Lookup source could be array or database
  • DO NOT use user input directly!