I never seen to be able to remember the fonts available on the iPhone. Here's the code to print out all font families and font styles.

for (NSString *familyName in [UIFont familyNames]) {
    NSLog(@"%@, %@", familyName, [UIFont fontNamesForFamilyName:familyName]);
}

And here is the current result:

2010-05-17 17:38:05.931 fonts[20843:207] AppleGothic, (
    AppleGothic
)
2010-05-17 17:38:05.932 fonts[20843:207] Hiragino Kaku Gothic ProN, (
    "HiraKakuProN-W6",
    "HiraKakuProN-W3"
)
2010-05-17 17:38:05.932 fonts[20843:207] Arial Unicode MS, (
    ArialUnicodeMS
)
2010-05-17 17:38:05.932 fonts[20843:207] Heiti K, (
    "STHeitiK-Medium",
    "STHeitiK-Light"
)
2010-05-17 17:38:05.932 fonts[20843:207] DB LCD Temp, (
    DBLCDTempBlack
)
2010-05-17 17:38:05.932 fonts[20843:207] Helvetica, (
    "Helvetica-Oblique",
    "Helvetica-BoldOblique",
    Helvetica,
    "Helvetica-Bold"
)
2010-05-17 17:38:05.932 fonts[20843:207] Marker Felt, (
    "MarkerFelt-Thin"
)
2010-05-17 17:38:05.933 fonts[20843:207] Times New Roman, (
    TimesNewRomanPSMT,
    "TimesNewRomanPS-BoldMT",
    "TimesNewRomanPS-BoldItalicMT",
    "TimesNewRomanPS-ItalicMT"
)
2010-05-17 17:38:05.933 fonts[20843:207] Verdana, (
    "Verdana-Bold",
    "Verdana-BoldItalic",
    Verdana,
    "Verdana-Italic"
)
2010-05-17 17:38:05.933 fonts[20843:207] Georgia, (
    "Georgia-Bold",
    Georgia,
    "Georgia-BoldItalic",
    "Georgia-Italic"
)
2010-05-17 17:38:05.933 fonts[20843:207] Arial Rounded MT Bold, (
    ArialRoundedMTBold
)
2010-05-17 17:38:05.933 fonts[20843:207] Trebuchet MS, (
    "TrebuchetMS-Italic",
    TrebuchetMS,
    "Trebuchet-BoldItalic",
    "TrebuchetMS-Bold"
)
2010-05-17 17:38:05.933 fonts[20843:207] Heiti TC, (
    "STHeitiTC-Light",
    "STHeitiTC-Medium"
)
2010-05-17 17:38:05.933 fonts[20843:207] Geeza Pro, (
    "GeezaPro-Bold",
    GeezaPro
)
2010-05-17 17:38:05.934 fonts[20843:207] Courier, (
    Courier,
    "Courier-BoldOblique",
    "Courier-Oblique",
    "Courier-Bold"
)
2010-05-17 17:38:05.934 fonts[20843:207] Arial, (
    ArialMT,
    "Arial-BoldMT",
    "Arial-BoldItalicMT",
    "Arial-ItalicMT"
)
2010-05-17 17:38:05.934 fonts[20843:207] Heiti J, (
    "STHeitiJ-Medium",
    "STHeitiJ-Light"
)
2010-05-17 17:38:05.934 fonts[20843:207] Arial Hebrew, (
    ArialHebrew,
    "ArialHebrew-Bold"
)
2010-05-17 17:38:05.934 fonts[20843:207] Courier New, (
    "CourierNewPS-BoldMT",
    "CourierNewPS-ItalicMT",
    "CourierNewPS-BoldItalicMT",
    CourierNewPSMT
)
2010-05-17 17:38:05.934 fonts[20843:207] Zapfino, (
    Zapfino
)
2010-05-17 17:38:05.934 fonts[20843:207] American Typewriter, (
    AmericanTypewriter,
    "AmericanTypewriter-Bold"
)
2010-05-17 17:38:05.935 fonts[20843:207] Heiti SC, (
    "STHeitiSC-Medium",
    "STHeitiSC-Light"
)
2010-05-17 17:38:05.935 fonts[20843:207] Helvetica Neue, (
    HelveticaNeue,
    "HelveticaNeue-Bold"
)
2010-05-17 17:38:05.935 fonts[20843:207] Thonburi, (
    "Thonburi-Bold",
    Thonburi
)

Getting ImageMagick to work by calling system() in PHP turned out to be more troublesome that originally assumed. Of course, Safe-Mode has be off, the dirs need to have the appropriate permission, and the absolute paths to 'convert' and your files should be set.

But still, it would not work. Despite executing directly in the shell quite nicely. The revelation came late, but better than never:

IM apparently hate single quote ' ', and absolutely insists on double quotes " " to wrap it's arguments in.

Can not really say, that this is well thought out... Anyways...