How do I read any request header in PHP

Question

How should I read any header in PHP   For example the custom header  X-Requested-With

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SERVER  HTTP X REQUESTED WITH     RFC3875  4 1 18      Meta-variables with names beginning with HTTP  contain values read from the client request header fields  if the protocol used is HTTP  The HTTP header field name is converted to upper case  has all occurrences of - replaced with   and has HTTP  prepended to give the meta-variable name

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Pass a header name to this function to get its value without using for loop  Returns null if header not found           var string  headerName case insensitive header name        return string null header value or null if not found     function get header  headerName         headers   getallheaders        return isset  headerName     headers  headerName    null      Note  this works only with Apache server  see  http   php net manual en function getallheaders php  Note  this function will process and load all of the headers to the memory and it s less performant than a for loop

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This small PHP snippet can be helpful to you    lt  php foreach   SERVER as  key   gt   value   echo    SERVER     key          value   lt br   gt        gt

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Here s how I m doing it  You need to get all headers if  header name isn t passed    lt  php function getHeaders  header name null         keys array keys   SERVER        if is null  header name                  headers preg grep    HTTP      si    keys         else                header name safe str replace  -        strtoupper preg quote  header name                  headers preg grep    HTTP   header name safe   si    keys              foreach  headers as  header                if is null  header name                         headervals substr  header  5     SERVER  header                 else                       return   SERVER  header                            return  headervals    print r getHeaders     echo   n n  getHeaders  Accept-Language      gt    It looks a lot simpler to me than most of the examples given in other answers   This also gets the method  GET POST etc   and the URI requested when getting all of the headers which can be useful if you re trying to use it in logging   Here s the output   Array    HOST    gt  127 0 0 1  USER AGENT    gt  Mozilla 5 0  X11  Ubuntu  Linux x86 64  rv 28 0  Gecko 20100101 Firefox 28 0  ACCEPT    gt  text html application xhtml xml application xml q 0 9     q 0 8  ACCEPT LANGUAGE    gt  en-US en q 0 5  ACCEPT ENCODING    gt  gzip  deflate  COOKIE    gt  PHPSESSID MySessionCookieHere  CONNECTION    gt  keep-alive    en-US en q 0 5

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PHP 7  Null Coalesce Operator     http    SCRIPT NAME    http    X REQUESTED WITH    http   strtoupper  http    header     SERVER  HTTP    http       SERVER  http     NULL   if is null  header        die  http    Not Found      echo  header

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I was using CodeIgniter and used the code below to get it  May be useful for someone in future    this- gt input- gt get request header  X-Requested-With

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function getCustomHeaders          headers   array        foreach   SERVER as  key   gt   value                if preg match    HTTP X      key                headers  key     value            return  headers      I use this function to get the custom headers  if the header starts from  HTTP X   we push in the array

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if only one key is required to retrieved  For example  Host  address is required  then we can use   apache request headers    Host     So that we can avoid loops and put it inline to the echo outputs

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To make things simple  here is how you can get just the one you want   Simple    headerValue     SERVER  HTTP X REQUESTED WITH      or when you need to get one at a time    lt  php         param  pHeaderKey     return mixed     function get header   pHeaderKey            Expanded for clarity       headerKey   str replace  -         pHeaderKey        headerKey   strtoupper  headerKey        headerValue   NULL         Uncomment the if when you do not want to throw an undefined index error         I leave it out because I like my app to tell me when it can t find something I expect        if   array key exists  headerKey    SERVER           headerValue     SERVER   headerKey                return  headerValue       X-Requested-With mainly used to identify Ajax requests  Most JavaScript frameworks    send this header with value of XMLHttpRequest  so this will not always be present   header x requested with   get header   X-Requested-With       The other headers are also in the super global array   SERVER  you can read about how to get at them here  http   php net manual en reserved variables server php

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This work if you have an Apache server  PHP Code    headers   apache request headers     foreach   headers as  header   gt   value        echo   header   value  lt br   gt  n       Result   Accept      Accept-Language  en-us Accept-Encoding  gzip  deflate User-Agent  Mozilla 4 0 Host  www example com Connection  Keep-Alive

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Here is an easy way to do it      echo get header  X-Requested-With    function get header  field         headers   headers list        foreach   headers as  header            list  key   value    preg split     s      header           if   key     field              return  value

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strtolower is lacking in several of the proposed solutions  RFC2616  HTTP 1 1  defines header fields as case-insensitive entities   The whole thing  not just the value part   So suggestions like only parsing HTTP  entries are wrong   Better would be like this   if   function exists  getallheaders          foreach    SERVER as  name   gt   value               RFC2616  HTTP 1 1  defines header fields as case-insensitive entities             if  strtolower substr  name  0  5       http                   headers str replace       -   ucwords strtolower str replace           substr  name  5          value                       this- gt request headers    headers    else        this- gt request headers   getallheaders        Notice the subtle differences with previous suggestions   The function here also works on php-fpm   nginx

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Since PHP 5 4 0 you can use getallheaders function which returns all request headers as an associative array   var dump getallheaders         array 8            Accept    gt        string 63   text html               Accept-Charset    gt        string 31   ISSO-8859-1               Accept-Encoding    gt        string 17   gzip deflate sdch          Accept-Language    gt        string 14   en-US en q 0 8          Cache-Control    gt        string 9   max-age 0          Connection    gt        string 10   keep-alive          Host    gt        string 9   localhost          User-Agent    gt        string 108   Mozilla 5 0  Windows NT 6 1  WOW64                Earlier this function worked only when PHP was running as an Apache NSAPI module

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You should find all HTTP headers in the   SERVER global variable prefixed with HTTP  uppercased and with dashes  -  replaced by underscores       For instance your X-Requested-With can be found in     SERVER  HTTP X REQUESTED WITH     It might be convenient to create an associative array from the   SERVER variable  This can be done in several styles  but here s a function that outputs camelcased keys    headers   array    foreach    SERVER as  key   gt   value        if  strpos  key   HTTP        0             headers str replace          ucwords str replace           strtolower substr  key  5          value            Now just use  headers  XRequestedWith   to retrieve the desired header   PHP manual on   SERVER  http   php net manual en reserved variables server php

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IF  you only need a single header  instead of all headers  the quickest method is    lt  php    Replace XXXXXX XXXX with the name of the header you need in UPPERCASE  and with  -  replaced by       headerStringValue     SERVER  HTTP XXXXXX XXXX       ELSE IF  you run PHP as an Apache module or  as of PHP 5 4  using FastCGI  simple method    apache request headers     lt  php  headers   apache request headers     foreach   headers as  header   gt   value        echo   header   value  lt br   gt  n        ELSE  In any other case  you can use  userland implementation     lt  php function getRequestHeaders          headers   array        foreach   SERVER as  key   gt   value            if  substr  key  0  5   lt  gt   HTTP                  continue                     header   str replace       -   ucwords str replace           strtolower substr  key  5                headers  header     value            return  headers      headers   getRequestHeaders     foreach   headers as  header   gt   value        echo   header   value  lt br   gt  n        See Also  getallheaders   -  PHP    5 4  cross platform edition Alias of apache request headers    apache response headers   - Fetch all HTTP response headers  headers list   - Fetch a list of headers to be sent

[php] How do I read any request header in PHP

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