PHP Strings

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PHP Strings

• A string can be single- or double-quoted.
• An extensive set of functions for strings are
  provided
• Manipulation with a regular expression,
• Conversion between a string and an array,
• Outputing by echo(), print(), printf(), and
  print_r(), and
• Others

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Single-Quoted String

• No evaluation occurs for a single-quoted string.

age 20 echo I am age.\n echo
Single echo \Double\ echo
Double echo age gt 18 ? OK
I am age.\n (illegal) \Double\ Double OK
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Double-Quoted String

• Variables and escape sequences within a
  double-quoted
• string are evaluated or replaced.

age 20 echo I am age.\n echo
Single\n echo \Double\\n echo
Double echo age gt 18 ? OK
I am 20. Single Double (illegal) OK
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int strlen(string)

• Returns the length of string string.

str 'Hello' len strlen(str) echo len
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int strpos(string1, string2)

• Returns the numeric position of string2 in
• string1.

str My dog house.' position
strpos(str, dog) echo position
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int strpos(str1, str2 ) Warning

• Returns false if str2 is not a substring of
  str1.
• Returns 0 if str2 is at the beginning of str1,
  so using if(strpos(str1, str2) 0) could
  cause an unreliable result.
• if(strpos(str1, str2) 0) may be used.

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string substr(string, start) Substring
Returns the string present in string starting
from location start until end of string.

• str My dog.
• str2 substr(str, 3)
• echo str2
• str3 substr(str1, 3, 2)
• echo str3

dog. do
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string strstr(string1, string2) and stristr()
Finds the location of string2 within string1, and
returns the remaining part of string1 from
that location. strstr is case-sensitive stristr
is not

• str This is Department of EECS.
• str2 strstr(str, Depart)
• echo str2

Department of EECS.
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array explode(delim, string)
Creates an array of the substrings in
string, separated by delim.

• str Kelley Engineering Center
• arr explode(" ", str)
• echo arr0\narr1\narr2\n

Kelley Engineering Center
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string implode(delim, array)
Creates a string out of the elements in
array, connected by delim.

• arr array(S10', Wolf, 20)
• string implode(', arr)
• echo string

S10Wolf20
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int ereg(pattern, string, array) Pattern
Matching I
Tests whether or not string matches
regular expression pattern.

• ereg(boy', cowboys')
• ereg('boy', cowboys')
• ereg('cow', cowboys')
• ereg(cow', 'cowboys')
• ereg(boys', 'cowboys')

true false true false true
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int ereg(pattern, string, array) Pattern
Matching II
Wild card characters.

• ereg(.', cowboys')
• ereg(. . . . . . .', cowboys')
• ereg('c.s', cowboys')
• ereg('c.s', cowgirls')
• ereg('c.s', tomboys')
• ereg(ab', aaabb')
• ereg(ab', bbbb')
• ereg(ab', ccbbb')
• ereg(ab', aabbb')
• ereg(ab', bbb')

true true true true false true true false true fal
se
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int ereg(pattern, string, array) Pattern
Matching III
Specifying a range or set of valid characters.

• ereg(a-z', cowboy')
• ereg(a-z', cowboy123')
• ereg(a-z0-9', cowboy123')
• ereg(a-z6', cowboy')
• ereg(a-z4', cowboy')
• ereg(bcowy', cowboy')

true false true true false true
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Extracting Substrings
Retrieving text in groups.

• email minoura_at_eecs.orst.edu
• ereg('(.)_at_(.)', email, arr)
• echo Match arr0\n
• echo Host arr1\n
• echo Host arr2\n

Match minoura_at_eecs.orst.edu User minoura Host
eecs.orst.edu
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Extracting Substrings
Retrieving text in groups.

• email minoura_at_eecs.orst.edu
• ereg('(.)_at_(.)', email, arr)
• echo Match arr0\n
• echo Host arr1\n
• echo Host arr2\n

Match minoura_at_eecs.orst.edu User minoura Host
eecs.orst.edu
PHP String
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Meta Characters for a Regular Expression
The following meta characters can be used in a
regular expression.

• - start of line, or negation of
• characters
• - end of line
• . - any character
• range, or set of characters
• () grouping
• - any number of times
• - at least once
• ? - exactly once
• n, m match n through m occurrences