What is the difference between single-quoted and double-quoted strings in PHP

Question

I m a little confused why I see some code in PHP with string placed in single quotes and sometimes in double quotes   I just know in  NET  or the C language  if it is in a single quote  that means it is a character  not a string

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Example of single  double  heredoc  and nowdoc quotes  lt  php       fname    quot David quot           Single quotes     echo  My name is  fname       My name is  fname          Double quotes     echo  quot My name is  fname  quot      My name is David          Curly braces to isolate the name of the variable     echo  quot My name is   fname   quot      My name is David          Example of heredoc     echo  foo    lt  lt  lt abc     My name is   fname      abc              Example of nowdoc         echo  lt  lt  lt   abc          My name is  quot  name quot           Now  I am printing some     abc     gt

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Here some possibilities of single and double quotes with variable   world    world     Hello    world        hello    world

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PHP strings can be specified not just in two ways  but in four ways    Single quoted strings will display things almost completely  as is   Variables and most escape sequences will not be interpreted  The exception is that to display a literal single quote  you can escape it with a back slash     and to display a back slash  you can escape it with another backslash     So yes  even single quoted strings are parsed   Double quote strings will display a host of escaped characters  including some regexes   and variables in the strings will be evaluated  An important point here is that you can use curly braces to isolate the name of the variable you want evaluated  For example let s say you have the variable  type and you want to echo  The  types are   That will look for the variable  types  To get around this use echo  The   type s are  You can put the left brace before or after the dollar sign  Take a look at string parsing to see how to use array variables and such  Heredoc string syntax works like double quoted strings  It starts with  lt  lt  lt   After this operator  an identifier is provided  then a newline  The string itself follows  and then the same identifier again to close the quotation  You don t need to escape quotes in this syntax   Nowdoc  since PHP 5 3 0  string syntax works essentially like single quoted strings  The difference is that not even single quotes or backslashes have to be escaped  A nowdoc is identified with the same  lt  lt  lt  sequence used for heredocs  but the identifier which follows is enclosed in single quotes  e g   lt  lt  lt  EOT   No parsing is done in nowdoc    Notes  Single quotes inside of single quotes and double quotes inside of double quotes must be escaped    string    He said  What  s up      string    He said   What s up        Speed  I would not put too much weight on single quotes being faster than double quotes  They probably are faster in certain situations  Here s an article explaining one manner in which single and double quotes are essentially equally fast since PHP 4 3  Useless Optimizations toward the bottom  section C   Also  this benchmarks page has a single vs double quote comparison  Most of the comparisons are the same  There is one comparison where double quotes are slower than single quotes

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One thing    It is very important to note that the line with the closing identifier of Heredoc must contain no other characters  except a semicolon      That means especially that the identifier may not be indented  and there may not be any spaces or tabs before or after the semicolon   Example       str    lt  lt  lt EOD Example of string spanning multiple lines using heredoc syntax  EOD

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A single-quoted string does not have variables within it interpreted   A double-quoted string does   Also  a double-quoted string can contain apostrophes without backslashes  while a single-quoted string can contain unescaped quotation marks   The single-quoted strings are faster at runtime because they do not need to be parsed

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Both kinds of enclosed characters are strings   One type of quote is conveniently used to enclose the other type of quote        and        The biggest difference between the types of quotes is that enclosed identifier references are substituted for inside double quotes  but not inside single quotes

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Some might say that I m a little off-topic  but here it is anyway  You don t necessarily have to choose because of your string s content between  echo  quot It s   quot game  quot  time  quot   or echo  It  s  quot game quot  time    If you re familiar with the use of the english quotation marks  and the correct character for the apostrophe  you can use either double or single quotes  because it won t matter anymore  echo  quot It   s    game    time  quot   and echo  It   s    game    time    Of course you can also add variables if needed  Just don t forget that they get evaluated only when in double quotes

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Things get evaluated in double quotes but not in single    s    dollars   echo  This costs a lot of  s       This costs a lot of  s  echo  This costs a lot of  s       This costs a lot of dollars

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In PHP  single quote text is considered as string value and double quote text will parse the variables by replacing and processing their value    test    variable   echo  Hello Mr  test      the output would be  Hello Mr variable echo  Hello Mr  test      the output would be  Hello Mr  test   Here  double quote parse the value and single quote is considered as string value  without parsing the  test variable

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In PHP  both  my name  and  my name  are string  You can read more about it at the PHP manual   Thing you should know are   a    name    b    my  a       my name   c    my  a       my name    In PHP  people use single quote to define a constant string  like  a    my name    abc xyz   while using double quote to define a string contain identifier like  a  b  c  d    And other thing is    echo  my name     is faster than  echo  my name     but  echo  my      a    is slower than  echo  my  a     This is true for other used of string

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The difference between using single quotes and double quotes in php is that if we use single quotes in echo statement then it is treated as a string      but if we enter variable name within double quotes then it will output the value of that variable along with the string

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Single quoted  The simplest way to specify a string is to enclose it in single quotes  Single quote is generally faster  and everything quoted inside treated as plain string   Example   echo  Start with a simple string   echo  String  s apostrophe   echo  String with a php variable   name        Double quoted  Use double quotes in PHP to avoid having to use the period to separate code  Note  Use curly braces    to include variables if you do not want to use concatenation     operator  in string   Example   echo  Start with a simple string   echo  String s apostrophe   echo  String with a php variable   name        Is there a performance benefit single quote vs double quote in PHP   Yes  It is slightly faster to use single quotes   PHP won t use additional processing to interpret what is inside the single quote  when you use double quotes PHP has to parse to check if there are any variables within the string

[php] What is the difference between single-quoted and double-quoted strings in PHP?

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