PHP-Functions

This chapter shows you the main functions of PHP-Code Elements which can be used. The Introduction in PHP-Code will help you to integrate all PHP functions for your questionnaire.

At the very end of this page will be a helpful information how the documentation of the PHP-functions can be read: Function in Detail

See also filter questions und filters.

• value() – Use answer of participant, e.g. for a filter question
• goToPage() – Jump to another page immediately
  • goToPage('end') – End the current interview
• repeatPage() – Show recent page again
• redirect() – Redirect the respondent to a different website
• question() – Display a question within the questionnaire
• text() – Display a text element within the questionnaire
• debug() – Show content of a data or PHP variable

• option() – Modify page display settings (buttons, progress bar)
• preset() – Preset a response for a question
• markFail() – Set the marker “response missing” for an input
• prepare_input() – Prepare an input to be shown within another question
• html() – Output of HTML-Code within questionnaire
• textlink() – Create a hyperlink that shows a text element in a pop-up window
• buttonToPage() – Button to jump within the questionnaire
• buttonCode() – Create-HTML-Code for next/back button
• buttonHide() – Do not show back/next buttons at the page's bottom
• ​library()​ – Make a JavaScript or PHP library available
• pageCSS() – Add CSS instructions to a single questionnaire page
• pageHead() – Store meta-information about the questionnaire page

SoSci Survey supports several functions for random sampling or random group assignment (Randomization).

• put() – Save a value in the data set
• random() – Dice a random number (with replacement)
• random_p() – Random number in correlation to likelihood
• random_items() – Randomly select items from a list
• randomUse() – Storing slips of paper from a random number generator
• urnDraw() – Draw out from urn (random selection without replacement)
• urnPutAway() – Put away the chit drawn via urnDraw()
• urnStatus() – Retrieve current status of an urn

• registerVariable() – Register PHP-Variable for following sites
• ​id()​ – Create a question or variable label from it's components
• replace() – Prepare a placeholder
• getItems() – Order items of question by selected rules
• getQuestions() – Enlist a section's questions
• getItemtext() – Retrieve the text of a specific items or option
• getValueText() – Retrieve the label of a response code/option
• getTextElement() – Retrieve the content of a text element
• getRoute() – Tell if the next or back button was hit previously
• caseNumber() – Number of actual interviews
• caseSerial() – Serial number used in interview
• caseTime() – Show length of stay on one or more sites
• caseToken() – Identification of interview
• reference() – Ask for reference (within link to questionnaires)
• serialCheck() – Ask for serial number
• readGET() – Read converted variable from link
• sendJSON() – Send HTTP request in JSON format (REST API)
• sendPOST() – Send HTTP request in POST format (REST API)
• sendXML() – Send HTTP request in XML format (REST API)
• getAnswerMissing() – Information for site repeat if questions was obligated
• listFails() – List of not responded obligation questions
• setNextPage() – Set side for click on ,,go further“
• setPageOrder() – Change the order to display subsequent questionnaire pages
• loopPage() – Show a page multiple times in a loop
• ​loopToPage()​ – Show multiple pages multiple times in a loop
• pageStop() – Do not show any further contents on the questionnaire page
• getLanguage() – Determine language
• setLanguage() – Change language

• goToQuestionnaire() – Jump from one Questionaire to the next (once)
• goToParent() – Go back to the formerly Questionaire
• multiLevelDown() – Start a sub-questionaire inside the main questionaire (if necessary also several times)
• multiLevelData() – Get data specified in multiLevelDown()
• multiLevelReturn() – Return from the sub-questionnaire to the main questionnaire
• multiLevelResponse() – Get data specified in multiLevelReturn()
• multilevelput – Write a value directly into the higher-level record
• multiLevelURL() – Create a URL for a sub-questionnaire to be used later

• dbGet() – Read data from date base
• dbKeys() – List key for data base
• dbLoad() – Call all entries with defined prefix from the contents database
• dbSet() – Safe data in data base
• dbTouch() – Refresh time-stamp for data base entry

• dropValue() – Delete a single variable from the current interview
• dropCase() – Mark the current interview for deletion
• dropHistory() – Delete the page history of the current interview

• statistic() – Simple statistical analysis of all data
• diagram() – Simple diagram (e. g. frequency) for all analyzed data

• answers() – Show a question including the respondent's answers
• answersOption() – Adjust display of answers via answers() or answersPrint()
• answersPrint() – Display all questions of a questionnaire segment including the respondent's answers
• info() – Meta informationen about the current interview case or the display mode
• valueSum() – Compute sum over scale or variables
• valueMean() – Compute mean over scale or variable
• valueSD() – Compute standard deviation over scale or variable
• valueVar() – Compute variance over scale or variable
• convertDateTime() – Convert date/time texts (strings) and timestamps

• diagram2() – Create diagram with set data
• getQRCodeImage() – Integrate QR Code in the questionnaire
• imagepng_embed() – Include a PNG graphic without storing it to a file

• mailResume() – Resume an interview after a given delay
• mailSchedule() – Schedule to send a mailing to a single recipient
• mailRevoke() – Cancel a scheduled mailing
• panelData() – Resolve information on the address record

PHP provides a number of helpful functions, which can easily be used during questionnaire PHP Manual documented.

• Useful functions in general
  • implode - Array-Fusion of elements to string
  • explode - Split string into array
  • preg_split - Split string with regular expression into array

• Mathematical functions
  • round - Circular from comma
  • ceil - Round up
  • floor - Round down
  • abs - Find amount of number

• Array-Functions
  • array_diff - Subtract array-elements
  • array_fill - Fill array with (same) values
  • array_flip - Exchange key and values within array
  • array_intersect - Intersection between arrays
  • array_keys - determine key of arrays
  • array_key_exists - Check if function array-key exists
  • array_merge - Merge arrays
  • array_pop - Delete last element of arrays and show output
  • array_push - Insert element(s) at the end of arrays
  • array_rand - Random selection of one or more arrays
  • array_reverse - Reversed output of arrays
  • array_search - Search value within array
  • array_shift - Cut element at the beginning of array and provide output
  • array_slice - Write array slice into new array
  • array_sum - Sum elements in array
  • array_unique - Delete counterpart elements from array
  • array_unshift - Set value(s) on top of the array
  • array_values - Transform associative into indexed array
  • arsort - Sort array downwards and keep key
  • count - Output count of elements in array
  • in_array - Check if value is available in array
  • is_array - Check if variable is a array
  • krsort - Sort array downwards by keys
  • ksort - Sort array upwards by keys
  • list - Spread array on several variables
  • rsort - Sort array downwards
  • shuffle - Sort array randomly
  • sort - Sort array upwards
• Date and Time
  • date - Format timestamp as date output
  • mktime - Code time measurement into timestamp
  • microtime - Output of microseconds in timestamp
  • time - Output of seconds in timestamp
• String-Settings
  • htmlentities - Transform all characters which have HTML entities
  • htmlspecialchars - Transform HTML-Syntax-codes (inverted comma, top brackets) into HTML entities
  • ltrim - Delete space at the beginning of strings
  • number_format - Format number after comma
  • rtrim - Delete space at the end of strings
  • str_pad - Fill string length to individual size
  • str_replace - Search part string and replace
  • strlen - Determine string length
  • strtolower - transform sting into lower case
  • strtoupper - Transform string in capitals
  • substr_count - Count frequency of part strings
  • substr - Detect part strings
  • trim - Delete space at beginning and end
  • Also allowed are the functions: nl2br, str_repeat, str_shuffle, str_word_count, strip_tags, stripos, stristr, strpos, strrev, strripos, strrpos, strstr, substr_replace, wordwrap
    
• Drawings (e.g. diagrams)
  • imagecolorallocate - Use color for graphic
  • imagecreate - Create new picture
  • imagecreatetruecolor - New picture in real color (16 Mio.) sings
  • imageellipse - Draw ellipse or circle
  • imagefill - Fill picture (range) with color
  • imagefilledarc - Draw filled circle (sector)
  • imagefilledellipse - Draw filled ellipse or circle
  • imagefilledpolygon - Draw filled polygon
  • imagefilledrectangle - Draw filled rectangle
  • imagefilltoborder - Fill picture with color until line
  • imageline - Draw straight line
  • imagepolygon - Draw polygon
  • imagerectangle - Draw rectangle
  • imagesetbrush - Set brush
  • imagesetpixel - Pixel sign
  • imagesetstyle - Set line style
  • imagesetthickness - Set line width
  • imagestring - Text sign (horizontal)
  • More allowed functions: image_type_to_extension, image_type_to_mime_type, imagearc, imagechar, imagecharup, imagecolorallocatealpha, imagecolorat, imagecolorclosest, imagecolorclosestalpha, imagecolorclosesthwb, imagecolordeallocate, imagecolorexact, imagecolorresolve, imagecolorset, imagecopy, imagecopymerge, imagecopymergegray, imagecopyresampled, imagecopyresized, imagedashedline, imagedestroy, imagefilter, imagefontheight, imagefontwidth, imageinterlace, imagepalettecopy, imagerotate, imagesavealpha, imagesettile, imagestringup, imagesx, imagesy, imagetruecolortopalette
  • Following functions can be used in modified version: imagepng, imagettftext, imagecreatefrompng
• Miscellaneous
  • intval - Convert Variable into integer value
  • md5 - Compute MD5-hash

Some functions pose a security risk or do not work as expected in the context of the questionnaire. Alternatives are listed below. If you need additional features, please let SoSci Survey know.

• echo
  • html()
  • text()
• mysqld_query()
  • Database for Contents
  • datasetRetrieve()

Reference-syntax for each function, e.g.:

void set(mixed Value, [string Memory])

This reference-syntax describes the argumentation of functions and it's data type.

• At the beginning return function of data type is shown void, meaning: function is acting but does not return values.
• Arguments listed in braces. Optional arguments in angled braces. Function set() has o have at least one argument Value than it is allowed to use another (second) argument Memory .
• Type of data stands in front of argument:
  • mixed means different types of data are allowed
  • int is a number
  • string text with inverted comma
  • array List of values (Arrays)