What is cURL in PHP?

This article is the first part of the series using curl in php, if you know the basic you can visit Sending post request using curl.

cURL

It is a library that helps to receive or transfer data using protocols like DICT, FILE, FTP, FTPS, GOPHER, HTTP, HTTPS, IMAP, IMAPS, LDAP, LDAPS, POP3, POP3S, RTMP, RTSP, SCP, SFTP, SMB, SMBS, SMTP, SMTPS, TELNET and TFTP.

php-curl

cURL in PHP

It is a library used to make HTTP request in PHP.In layman terms, cURL gives the same effect as a user opening a web page in the browser after disabling javascript.When a HTTP request is made in php using curl then the received content contains the source code of the page(after disabling javascript).cURL is a resource, a resource in php is a reference to a data hold by some other module.

Installation of cURL in php can be seen at php.net

Let’s begin with an example to understand curl functionality practically.

Variable $output contains the source code of the web page http://tusharsharma.in. Now let’s take out title of the page using regular expression.

Above code outputs string(45) “Tushar Sharma | Technophile and PHP developer”.Here we take output as a string and pass in the preg_match and get title of the page.

To get information about any curl request we use a function curl_getinfo(curl resource). This function gives output as follows which contains information about content/type, http code, header size, port, content length and several other parameters related to our request.

Some important cURL options are as follows:

– maximum time required to make a connection to a server
curl_setopt($ch,CURLOPT_CONNECTTIMEOUT , 10 );

– maximum amount of time in seconds to which the execution of individual cURL extension function calls will be limited
curl_setopt($ch,CURLOPT_TIMEOUT , 55 );

– follow url after redirection
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);

– verify the certificate’s name against host
curl_setopt($ch , CURLOPT_SSL_VERIFYHOST , true);

– verify the peer’s SSL certificate
curl_setopt($ch , CURLOPT_SSL_VERIFYPEER , true);

– set useragent of the browser to check how webpage looks in that particular browser
curl_setopt($ch, CURLOPT_USERAGENT , Mozilla/5.0 (Windows NT 6.1; WOW64; rv:42.0) Gecko/20100101 Firefox/42.0 );

– file name to store cookies to
curl_setopt($ch, CURLOPT_COOKIEJAR, $cookie_location);

– file name to read cookies from
curl_setopt($ch, CURLOPT_COOKIEFILE, $cookie_location);

Error Handling

Mostly curl_error(curl resource) and curl_errorno(curl resource)are used to get error information during a curl session.curl_error  returns an error in the form of string and curl_errorno return error code.Also you can look for http code if you got any error.In case the request fails, http code could be 404, 503 or anything else but not 200.Check complete list of http code at Wikipedia.

cURL is a very useful library in php which can perform some cool stuff if used wisely.Hope you enjoy the tutorial and tell me what you have done using curl in php.

For detailed reading you can visit curl haxx and php.net.

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