10.2. Member Variable Notes
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## 10.2. Member Variable Notes

This section contains details on some of the PHPlot class member variables listed in the previous section. Remember that all PHPlot class member variables are meant for internal use only.

### 10.2.1. fonts[]

The `fonts[]` array contains information about the fonts to use for text on the plot. The array keys are the element names (such as `title` or `legend`) as used in SetFont, SetFontGD, or SetFontTTF. The array values are arrays which contain information about the font to use for that element. The keys and values of the second-level arrays are:

Key | Value for TTF | Value for GD Font
--- | --- | ---
ttf | True for a TrueType font | False for a GD font
font | Pathname of the font file | Font number: 1 through 5
size | Font point size | Not used
height | Height in pixels of an upper-case "E" in the font | Font height in pixels
width | Width in pixels of an upper-case "E" in the font. | Font width in pixels
spacing | Font's built-in inter-line spacing | Not used
line_spacing | User-requested inter-line spacing factor. | Same as for TTF

For TrueType fonts, the height and width can vary by character. The fonts array stores a height and width value for the font, but these are only used for sizing non-text plot elements (such as the legend color boxes). When PHPlot needs to know the drawn size of a string that will use TTF, it calculates the exact size of that specific string when drawn with the designated font.

GD fonts have fixed character width and height, so the values stored in the fonts array can be used to calculate text string sizes.

The `spacing` key stores the TrueType font's built-in inter-line spacing. Although TrueType fonts have this information internally, PHP cannot access it, so PHPlot calculates it by taking the height of the string "E\nE" and subtracting twice the height of the letter E.

The `line_spacing` key stores the user-specified line spacing adjustment for a text element, if any, from SetFont or one of the two related functions. It will be NULL if the spacing was not set for this element, meaning use the default line spacing. See SetLineSpacing for more information on how this is used.

Here is an example of part of a fonts array, for the title element:

    $plot->fonts['title'] = array(
        'ttf' => FALSE,          // This element uses a GD font
        'font' => 2,             // Use GD font 2
        'height' => 13,          // Provided by GD
        'width' => 6,            // Provided by GD
        'line_spacing' => NULL,  // Use default line spacing
    )

### 10.2.2. label_format[]

The `label_format[]` array contains information about how text labels should be formatted. This array has 4 entries, with keys 'x', 'y', 'xd', and 'yd'. The 'x' and 'y' entries are for tick labels, and the 'xd' and 'yd' entries are for data labels. (Note that PHPlot defaults data label formatting to match tick label formatting, but this is handled in CheckLabels, with the tick label format information copied to the data label format information if necessary.)

The value of each entry in `label_format` is an array containing formatting information. The arrays are empty by default, meaning there is no special formatting. If formatting has been enabled, for example with SetXLabelType, the arrays can contain the following keys and values:

Key | Used with type | Value
--- | --- | ---
type |  | Formatting type: data, time, printf, or custom.
precision | data | The number of decimal positions to produce.
prefix | data | A prefix string to append to the label (for example, a currency sign).
suffix | data | A suffix string to append to the label (for example, a currency sign or percent sign). This replaces data_units_text (which still works too).
time_format | time | The date/time format string for the PHP strftime() function.
printf_format | printf | The format string for the PHP printf() function.
custom_callback | custom | The function (or array with object and method name) to call to format the label.
custom_arg | custom | An additional argument to pass to the custom_callback function.

### 10.2.3. plots[]

The `plots[]` array contains information about known plot types. Essentially, it tells FindDataLimits and DrawGraph how to produce the main portion of the plot. This was added in PHPlot-5.3.0. This is a static member variable in the PHPlot class, so it must be accessed as `PHPlot::$plots` and not through an instance of the class. It has protected visibility, so is not accessible from outside the class or derived classes.

The array keys are the plot types (for example: 'bars', 'linepoints'). These must not include upper case letters. The values are arrays which contain information about the plot type. The keys and values of the second-level arrays are:

Key | Value
--- | ---
draw_method | Name of the PHPlot class method (function) to call to draw the 'insides' of the plot. This is the only required entry. The function is responsible for drawing everything inside the plot area. (That is, everything except the plot titles, axis lines, tick marks and tick labels, grid lines, and legend.)
draw_arg | Optional argument(s) for the drawing method named by draw_method. If present, this must be an array. Each element of the array is passed to the draw_method function as a separate argument. If this is not specified, the drawing method is called with no arguments. This is generally used to 'overload' drawing methods so they handle multiple similar plot types.
draw_axes | A flag to indicate if the X axis and Y axis should be drawn. The default is TRUE. This is set to FALSE for pie charts.
abs_vals | Special data processing flag. If TRUE, this tells FindDataLimits that the plot type will take the absolute value of all dependent variable values in the data array. FindDataLimits needs this information so it knows how to find the minimum and maximum values in the data array. The default if omitted is FALSE.
sum_vals | Special data processing flag. If TRUE, this tells FindDataLimits that the plot type will sum up the dependent variable values in each row of the data array. FindDataLimits needs this information so it knows how to find the minimum and maximum values in the data array. The default if omitted is FALSE. If both abs_vals and sum_vals are TRUE, this means the plot type sums up the absolute values from the data array. (The stackedarea plot type does this.)

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