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ECA 236

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ECA 236

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  1. ECA 236 Open Source Server Side Scripting PHP Regular Expressions Open Source Server Side Scripting

  2. regular expressions • pattern matching • define a pattern • compare it to a string • test for match • replace match if desired ^([0-9]{3})-( [0-9]{2})-( [0-9]{4})$ Open Source Server Side Scripting

  3. RE functions • 2 functions to search strings for a match • ereg( ) • performs a case sensitive search • eregi( ) • performs a case insensitive search • 2 functions to replace matched strings • ereg_replace( ) • performs a case sensitive search and replace • eregi_replace( ) • performs a case insensitive search and replace Open Source Server Side Scripting

  4. RE types • PCRE – Perl Compatible Regular Expression • more powerful • harder to learn • can be used on binary data • POSIX Extended • less powerful • a little slower • easier to learn than PCRE Open Source Server Side Scripting

  5. defining a pattern • a regular expression defines a pattern to search against • specific set of rules • simple to complex • simplest pattern to match is a string literal • single letter • string of letters Open Source Server Side Scripting

  6. defining a pattern cont … • for example • to search for the string “cak”, case insensitive • a match will be returned for the following strings $pattern = “cak”; I’m flying out of CAK on Wednesday. I took my baby to a cake walk Saturday night. Mud was caked to my dog’s belly. Open Source Server Side Scripting

  7. metacharacters • special symbols that have meaning beyond their literal meaning • a period means any single character • letter • number • space • symbol Open Source Server Side Scripting

  8. metacharacters cont … • the regular expression • will not match any of the previous examples, but will match $pattern = “ca.k”; She cackled like a chicken when I slipped. cask of Amontillado 300 meters off Cape Rocca K 2 conducts dive exercises. Open Source Server Side Scripting

  9. metacharacters cont … to match any of these metacharacters as a string literal, it must be escaped with a backslash Open Source Server Side Scripting

  10. metacharacters cont … • the carat and the dollar sign specify where characters must be found • ^ carat • following characters must be at the beginning of a string will matchbut not $pattern = “^mush.”; Mushrooms are yummy. I love yummy mushrooms. Open Source Server Side Scripting

  11. metacharacters cont … • $ dollar sign • preceding characters must be at the end of a string will matchbut not $pattern = “mush\.$”; I love fried mush. I love yummy mushrooms. Open Source Server Side Scripting

  12. metacharacters cont … • | pipe • OR will matchbut will also match $pattern = “t|f”; Number six is T. Do you know the answer to number six? Open Source Server Side Scripting

  13. metacharacters cont … • | pipe peccadillo • the regular expression will matchto match whole words, group them using parentheses $pattern = “true|false”; trufalse or truealse $pattern = “(true)|(false)”; Open Source Server Side Scripting

  14. matching functions • ereg( ) • performs a case sensitive search • eregi( ) • performs a case insensitive search • both functions return TRUE if a match is found ereg( “pattern” , “string” ); $pattern = “pattern”;$string = “string”; $ereg( $pattern, $string ); Open Source Server Side Scripting

  15. metacharacters cont … to match any of these metacharacters as a string literal, it must be escaped with a backslash Open Source Server Side Scripting

  16. metacharacters cont … • to match multiple occurrences of previous characters • ? question mark • 0 or 1 instance of previous characterwill match but not $pattern = “r?”; Mary is coming. Harry is coming. Arrrrfff, howled the dog. Open Source Server Side Scripting

  17. metacharacters cont … • * asterisk • 0 or more instances of previous characterwill match $pattern = “r*”; Bob is coming. Harry is coming. Arrrrfff, howled the dog. Open Source Server Side Scripting

  18. metacharacters cont … + plus sign • 1 or more instance of previous characterwill match but not $pattern = “r+”; Mary is coming. Arrrrfff, howled the dog. Bob is coming. Open Source Server Side Scripting

  19. metacharacters cont … • to match specific number of occurrences • {x} • exactly that number of the previous characterswill match but not $pattern = “v{3}?”; vvv vvvvvvv Open Source Server Side Scripting

  20. metacharacters cont … {x,y} • occurs between and including the 2 numberswill match but not $pattern = “a{2,4}?”; aaaaaaaaa aaaaaa Open Source Server Side Scripting

  21. metacharacters cont … {x,} • occurs at least the number of times indicatedwill match but not $pattern = “m{2,}?”; mmmmmmmmm m Open Source Server Side Scripting

  22. metacharacters cont … Open Source Server Side Scripting

  23. metacharacters cont … Open Source Server Side Scripting

  24. character classes • created by placing certain characters inside square brackets • use of a hyphen indicates a range • will match any lowercase letter between a – z • will match any uppercase letter between M – R $pattern = “[a-z]”; $pattern = “[M-R]”; Open Source Server Side Scripting

  25. character classes cont … • provide a range for numbers • combine character class with metacharacters $pattern = “[0-9]”; $pattern = “[1-9]”; $pattern = “[a-zA-Z]{2,4}”; Open Source Server Side Scripting

  26. character classes cont … • test for vowels • predefined character classes • test for any letter or number $pattern = “[aeiou]”; $pattern = “[aeiou]{2}”; $pattern = “[[:alnum:]]”; Open Source Server Side Scripting

  27. character classes cont … • test for any letter, lower or upper case • test for any tab or spaces • test for any number $pattern =“[[:alpha:]] ”; $pattern =“[[:blank:]] ”; $pattern = “[[:digit:]]”; Open Source Server Side Scripting

  28. character classes cont … • test for any lower case letter • test for any upper case letter • test for any punctuation characters $pattern =“[[:lower:]] ”; $pattern =“[[:upper:]] ”; $pattern = “[[:punct:]]”; Open Source Server Side Scripting

  29. character classes cont … • test for any white space • test for any three letter word • test for any combination of three numbers $pattern =“[[:space:]] ”; $pattern = “[[:space:]] [[:alpha:]]{3} [[:space:]]”; $pattern = “[[:digit:]]{3}”; Open Source Server Side Scripting

  30. character classes cont … • inside square brackets a carat ^ has special meaning • indicates exclusion • to test for social security number • ??? $pattern =“[^aeiou] ”; xxx-xx-xxxx $pattern = “^([0-9]{3})-( [0-9]{2})-( [0-9]{4})$”; “^\(?([0-9]{3})\)?(-|\.|[[:space:]]|/)?([0-9]{3})(-|\.|[[:space:]]|/)?([0-9]{4})$” Open Source Server Side Scripting

  31. phone number • phone • parentheses around area code are optional • set of three numbers, followed by three numbers, followed by four numbers • sets of numbers generally separated by hyphen, period, space, forward slash, nothing “^\(?([0-9]{3})\)?(-|\.|[[:space:]]|/)?([0-9]{3})(-|\.|[[:space:]]|/)?([0-9]{4})$” Open Source Server Side Scripting

  32. replacement functions • ereg_replace( ) • performs a case sensitive search and replace • eregi_replace( ) • performs a case insensitive search and replace • both functions take 3 parameters • pattern to be matched • replacement string • string to be tested Open Source Server Side Scripting

  33. replacement functions • both functions return TRUE if a match is found ereg_replace( “pattern”, “replacement”, “string” ); $pattern = “pattern”; $replacement = “replacement”;$string = “string”; $eregi_replace( $pattern, $replacement, $string ); Open Source Server Side Scripting